output_token.txt

[Practical]
 
Extraction
 
and
 
Reporting
 
Language
.
[5]
 
Perl
 
was
 
originally
 
developed
 
by
 
Larry
 
Wall
 
in
 
1987
 
as
 
a
 
general-purpose
 
Unix
 
scripting
 
language
 
to
 
make
 
report
 
processing
 
easier
.
[6]
 
Since
 
then
,

 
it
 
has
 
undergone
 
many
 
changes
 
and
 
revisions
 
and
 
became
 
popular
 
amongst
 
programmers
.

 
Larry
 
Wall
 
continues
 
to
 
oversee
 
development
 
of
 
the
 
core
 
language
,

 
and
 
its
 
upcoming
 
version
,

 
Perl
 
6
.

 
Perl
 
borrows
 
features
 
from
 
other
 
programming
 
languages
 
including
 
C
,

 
shell
 
scripting
 
(sh)
,

 
AWK
,

 
and
 
sed
.
[7]
 
The
 
language
 
provides
 
powerful
 
text
 
processing
 
facilities
 
without
 
the
 
arbitrary
 
data
 
length
 
limits
 
of
 
many
 
contemporary
 
Unix
 
tools
,
[8]
 
facilitating
 
easy
 
manipulation
 
of
 
text
 
files
.

 
Perl
 
gained
 
widespread
 
popularity
 
in
 
the
 
late
 
1990s
 
as
 
a
 
CGI
 
scripting
 
language
,

 
in
 
part
 
due
 
to
 
its
 
parsing
 
abilities
.

 
Its
 
place
 
was
 
later
 
taken
 
by
 
PHP
 
and
 
Perl
 
has
 
remained
 
unpopular
 
since
 
then
.
[9]


In
 
addition
 
to
 
CGI
,

 
Perl
 
is
 
used
 
for
 
system
 

+

 
administration
,

 
network
 
programming
,

 
finance
,

 
bioinformatics
,

 
and
 
other
 
applications
.

 
Perl
 
is
 
nicknamed
 
"the
 
Swiss
 
Army
 
chainsaw
 

,

 
full
 
Y2038
 
compliance
,

 
regex
 
conversion
 
overloading
,

 
DTrace
 
support
,

 
and
 
Unicode
 
5
.
2
.
[10]
 
On
 
January
 
21
,

 
2011
,

 
Perl
 
5
.
12
.
3
 
was
 
released
;

 
it
 
contains
 
updated
 
modules
 
and
 
some
 
documentation
 
changes
.
[11]
 
Version
 
5
.
12
.
4
 
was
 
released
 
on
 
June
 
20
,

 
2011
.



On
 
May
 
14
,

 
2011
,

 
Perl
 
5
.
14
 
was
 
released
,

 
the
 
-
 
latest
 
version
 
of
 
that
 
branch
,

 
5
.
14
.
2
,

 
being
 
released
 
on
 
September
 
26
,

 
2011
.



On
 
May
 
20
,

 
2012
,

 
Perl
 
5
.
16
 
was
 
released
.

 
Notable
 
new
 
features
 
include
 
the
 
ability
 
to
 
specify
 
a
 
given
 
version
 
of
 
perl
 
that
 
one
 
wishes
 
to
 
emulate
,

 
allowing
 
users
 
to
 
upgrade
 
their
 
version
 
of
 
perl
,

 
but
 
still
 
run
 
old
 
scripts
 
that
 
wold
 
normally
 
be
 
incompatible
.

 
[12]
.

 
Perl
 
5
.
16
 
also
 
updates
 
the
 
core
 
to
 






Name


Perl
 
was
 
originally
 
named
 
"Pearl"
.

 
Larry
 
Wall
 
wanted
 
to
 
give
 
the
 
language
 
a
 
short
 
name
 
with
 
positive
 
connotations
;

 
he
 
claims
 
that
 
he
 
considered
 
(and
 
rejected)
 
every
 
three-
 
and
 
four-letter
 
word
 
in
 
the
 
dictionary
.

 
He
 
also
 
considered
 
naming
 
it
 
after
 
his
 
wife
 
Gloria
.

 
Wall
 
discovered
 
the
 
existing
 
PEARL
 
programming
 
language
 
before
 
Perl's
 
official
 
release
 
and
 
changed
 
the
 
spelling
 
of
 
the
 
name
.
[13]


When
 
referring
 
to
 
the
 
language
,

 
the
 
name
 
is
 
normally
 
capitalized
 
(Perl)
 
as
 
a
 
proper
 
noun
.

 
When
 
referring
 
to
 
the
 
interpreter
 
program
 
itself
,

 
the
 
name
 
is
 
often
 
uncapitalized
 
(perl)
 
because
 
most
 
Unix-like
 
file
 
systems
 
are
 
case-sensitive
.

 
Before
 
the
 
release
 
of
 
the
 
first
 
edition
 
of
 
Programming
 
Perl
,

 
it
 
was
 
common
 
to
 
refer
 
to
 
the
 
language
 
as
 
perl
;

 
Randal
 
L
.

 
Schwartz
,

 
however
,

 
capitalized
 
the
 
language's
 
name
 
in
 
the
 
book
 
to
 
make
 
it
 
stand
 
out
 
better
 
when
 
typeset
.

 
This
 
case
 
distinction
 
was
 
subsequently
 
documented
 
as
 
canonical
.
[14]


There
 
is
 
some
 
contention
 
about
 
the
 
all-caps
 
spelling
 
"PERL"
,

 
which
 
the
 
documentation
 
declares
 
incorrect[14]
 
and
 
which
 
some
 
core
 
community
 
members
 
consider
 
a
 
sign
 
of
 
outsiders
.
[15]
 
The
 
name
 
is
 
occasionally
 
backronymed
 
as
 
Practical
 
Extraction
 
and
 
Report
 
Language
,

 
which
 
appears
 
at
 
the
 
top
 
of
 
the
 
documentation[13]
 
and
 
in
 
some
 
printed
 
literature
.
[16]
 
Several
 
backronyms
 
have
 
been
 
suggested
 
as
 
equally
 
canonical
,

 
including
 
Wall's
 
own
 
humorous
 
Pathologically
 
Eclectic
 
Rubbish
 
Lister
.
[17]
 
Indeed
,

 
Wall
 
claims
 
that
 
the
 
name
 
was
 
intended
 
to
 
inspire
 
many
 
different
 
expansions
.
[18]





Programming
 
Perl
,

 
published
 
by
 
O'Reilly
 
Media
,

 
features
 
a
 
picture
 
of
 
a
 
camel
 
on
 
the
 
cover
 
and
 
is
 
commonly
 
referred
 
to
 
as
 
the
 
"Camel
 
Book"
.
[19]
 
This
 
image
 
of
 
a
 
camel
 
has
 
become
 
an
 
unofficial
 
symbol
 
of
 
Perl
 
as
 
well
 
as
 
a
 
general
 
hacker
 
emblem
,

 
appearing
 
on
 
T-shirts
 
and
 
other
 
clothing
 
items
.



O'Reilly
 
owns
 
the
 
image
 
as
 
a
 
trademark
 
but
 
licenses
 
it
 
for
 
non-commercial
 
use
,

 
requiring
 
only
 
an
 
acknowledgement
 
and
 
a
 
link
 
to
 
www
.
perl
.
com
.

 
Licensing
 
for
 
commercial
 
use
 
is
 
decided
 
on
 
a
 
case
 
by
 
case
 
basis
.
[20]
 
O'Reilly
 
also
 
provides
 
"Programming
 
Republic
 
of
 
Perl"
 
logos
 
for
 
non-commercial
 
sites
 
and
 
"Powered
 
by
 
Perl"
 
buttons
 
for
 
any
 
site
 
that
 
uses
 
Perl
.
[20]





The
 
Perl
 
Foundation
 
owns
 
an
 
alternative
 
symbol
,

 
an
 
onion
,

 
which
 
it
 
licenses
 
to
 
its
 
subsidiaries
,

 
Perl
 
Mongers
,

 
PerlMonks
,

 
Perl
.
org
,

 
and
 
others
.
[21]
 
The
 
symbol
 
is
 
a
 
visual
 
pun
 
on
 
pearl
 
onion
.
[22]





Perl
 
is
 
a
 
general-purpose
 
programming
 
language
 
originally
 
developed
 
for
 
text
 
manipulation
,

 
but
 
as
 
of
 
2010
 
is
 
used
 
for
 
a
 
wide
 
range
 
of
 
tasks
 
including
 
system
 
administration
,

 
web
 
development
,

 
network
 
programming
,

 
games
,

 
bioinformatics
,

 
and
 
GUI
 
development
.



The
 
language
 
is
 
intended
 
to
 
be
 
practical
 
(easy
 
to
 
use
,

 
efficient
,

 
complete)
 
rather
 
than
 
beautiful
 
(tiny
,

 
elegant
,

 
minimal)
.
[23]
 
Its
 
major
 
features
 
include
 
support
 
for
 
multiple
 
programming
 
paradigms
 
(procedural
,

 
object-oriented
,

 
and
 
functional
 
styles)
,

 
reference
 
counting
 
memory
 
management
 
(without
 
a
 
cycle-detecting
 
garbage
 
collector)
,

 
built-in
 
support
 
for
 
text
 
processing
,

 
and
 
a
 
large
 
collection
 
of
 
third-party
 
modules
.



According
 
to
 
Larry
 
Wall
,

 
Perl
 
has
 
two
 
slogans
.

 
The
 
first
 
is
 
"There's
 
more
 
than
 
one
 
way
 
to
 
do
 
it"
,

 
commonly
 
known
 
as
 
TMTOWTDI
.

 
The
 
second
 
slogan
 
is
 
"Easy
 
things
 
should
 
be
 
easy
 
and
 
hard
 
things
 
should
 
be
 
possible"
.
[8]





Features


The
 
overall
 
structure
 
of
 
Perl
 
derives
 
broadly
 
from
 
C
.

 
Perl
 
is
 
procedural
 
in
 
nature
,

 
with
 
variables
,

 
expressions
,

 
assignment
 
statements
,

 
brace-delimited
 
blocks
,

 
control
 
structures
,

 
and
 
subroutines
.



Perl
 
also
 
takes
 
features
 
from
 
shell
 
programming
.

 
All
 
variables
 
are
 
marked
 
with
 
leading
 
sigils
,

 
which
 
unambiguously
 
identify
 
the
 
data
 
type
 
(for
 
example
,

 
scalar
,

 
array
,

 
hash)
 
of
 
the
 
variable
 
in
 
context
.

 
Importantly
,

 
sigils
 
allow
 
variables
 
to
 
be
 
interpolated
 
directly
 
into
 
strings
.

 
Perl
 
has
 
many
 
built-in
 
functions
 
that
 
provide
 
tools
 
often
 
used
 
in
 
shell
 
programming
 
(although
 
many
 
of
 
these
 
tools
 
are
 
implemented
 
by
 
programs
 
external
 
to
 
the
 
shell)
 
such
 
as
 
sorting
,

 
and
 
calling
 
on
 
system
 
facilities
.



Perl
 
takes
 
lists
 
from
 
Lisp
,

 
hashes
 
("associative
 
arrays")
 
from
 
AWK
,

 
and
 
regular
 
expressions
 
from
 
sed
.

 
These
 
simplify
 
and
 
facilitate
 
many
 
parsing
,

 
text-handling
,

 
and
 
data-management
 
tasks
.



Perl
 
5
 
added
 
features
 
that
 
support
 
complex
 
data
 
structures
,

 
first-class
 
functions
 
(that
 
is
,

 
closures
 
as
 
values)
,

 
and
 
an
 
object-oriented
 
programming
 
model
.

 
These
 
include
 
references
,

 
packages
,

 
class-based
 
method
 
dispatch
,

 
and
 
lexically
 
scoped
 
variables
,

 
along
 
with
 
compiler
 
directives
 
(for
 
example
,

 
the
 
strict
 
pragma)
.

 
A
 
major
 
additional
 
feature
 
introduced
 
with
 
Perl
 
5
 
was
 
the
 
ability
 
to
 
package
 
code
 
as
 
reusable
 
modules
.

 
Larry
 
Wall
 
later
 
stated
 
that
 
"The
 
whole
 
intent
 
of
 
Perl
 
5's
 
module
 
system
 
was
 
to
 
encourage
 
the
 
growth
 
of
 
Perl
 
culture
 
rather
 
than
 
the
 
Perl
 
core
.
"[24]


All
 
versions
 
of
 
Perl
 
do
 
automatic
 
data-typing
 
and
 
automatic
 
memory-management
.

 
The
 
interpreter
 
knows
 
the
 
type
 
and
 
storage
 
requirements
 
of
 
every
 
data
 
object
 
in
 
the
 
program
;

 
it
 
allocates
 
and
 
frees
 
storage
 
for
 
them
 
as
 
necessary
 
using
 
reference
 
counting
 
(so
 
it
 
cannot
 
deallocate
 
circular
 
data
 
structures
 
without
 
manual
 
intervention)
.

 
Legal
 
type-conversions
 
—
 
for
 
example
,

 
conversions
 
from
 
number
 
to
 
string
 
—
 
are
 
done
 
automatically
 
at
 
run
 
time
;

 
illegal
 
type
 
conversions
 
are
 
fatal
 
errors
.






Design


The
 
design
 
of
 
Perl
 
can
 
be
 
understood
 
as
 
a
 
response
 
to
 
three
 
broad
 
trends
 
in
 
the
 
computer
 
industry:
 
falling
 
hardware
 
costs
,

 
rising
 
labor
 
costs
,

 
and
 
improvements
 
in
 
compiler
 
technology
.

 
Many
 
earlier
 
computer
 
languages
,

 
such
 
as
 
Fortran
 
and
 
C
,

 
aimed
 
to
 
make
 
efficient
 
use
 
of
 
expensive
 
computer
 
hardware
.

 
In
 
contrast
,

 
Perl
 
is
 
designed
 
to
 
make
 
efficient
 
use
 
of
 
expensive
 
computer-programmers
.



Perl
 
has
 
many
 
features
 
that
 
ease
 
the
 
task
 
of
 
the
 
programmer
 
at
 
the
 
expense
 
of
 
greater
 
CPU
 
and
 
memory
 
requirements
.

 
These
 
include
 
automatic
 
memory
 
management
;

 
dynamic
 
typing
;

 
strings
,

 
lists
,

 
and
 
hashes
;

 
regular
 
expressions
;

 
introspection
;

 
and
 
an
 
eval()
 
function
.

 
Perl
 
follows
 
the
 
theory
 
of
 
"no
 
built-in
 
limits"
,
[19]
 
an
 
idea
 
similar
 
to
 
the
 
Zero
 
One
 
Infinity
 
rule
.



Wall
 
was
 
trained
 
as
 
a
 
linguist
,

 
and
 
the
 
design
 
of
 
Perl
 
is
 
very
 
much
 
informed
 
by
 
linguistic
 
principles
.

 
Examples
 
include
 
Huffman
 
coding
 
(common
 
constructions
 
should
 
be
 
short)
,

 
good
 
end-weighting
 
(the
 
important
 
information
 
should
 
come
 
first)
,

 
and
 
a
 
large
 
collection
 
of
 
language
 
primitives
.

 
Perl
 
favors
 
language
 
constructs
 
that
 
are
 
concise
 
and
 
natural
 
for
 
humans
 
to
 
write
,

 
even
 
where
 
they
 
complicate
 
the
 
Perl
 
interpreter
.



Perl
 
syntax
 
reflects
 
the
 
idea
 
that
 
"things
 
that
 
are
 
different
 
should
 
look
 
different
.
"[25]
 
For
 
example
,

 
scalars
,

 
arrays
,

 
and
 
hashes
 
have
 
different
 
leading
 
sigils
.

 
Array
 
indices
 
and
 
hash
 
keys
 
use
 
different
 
kinds
 
of
 
braces
.

 
Strings
 
and
 
regular
 
expressions
 
have
 
different
 
standard
 
delimiters
.

 
This
 
approach
 
can
 
be
 
contrasted
 
with
 
languages
 
such
 
as
 
Lisp
,

 
where
 
the
 
same
 
S-expression
 
construct
 
and
 
basic
 
syntax
 
are
 
used
 
for
 
many
 
different
 
purposes
.



Perl
 
does
 
not
 
enforce
 
any
 
particular
 
programming
 
paradigm
 
(procedural
,

 
object-oriented
,

 
functional
,

 
or
 
others)
 
or
 
even
 
require
 
the
 
programmer
 
to
 
choose
 
among
 
them
.



There
 
is
 
a
 
broad
 
practical
 
bent
 
to
 
both
 
the
 
Perl
 
language
 
and
 
the
 
community
 
and
 
culture
 
that
 
surround
 
it
.

 
The
 
preface
 
to
 
Programming
 
Perl
 
begins:
 
"Perl
 
is
 
a
 
language
 
for
 
getting
 
your
 
job
 
done
.
"[8]
 
One
 
consequence
 
of
 
this
 
is
 
that
 
Perl
 
is
 
not
 
a
 
tidy
 
language
.

 
It
 
includes
 
many
 
features
,

 
tolerates
 
exceptions
 
to
 
its
 
rules
,

 
and
 
employs
 
heuristics
 
to
 
resolve
 
syntactical
 
ambiguities
.

 
Because
 
of
 
the
 
forgiving
 
nature
 
of
 
the
 
compiler
,

 
bugs
 
can
 
sometimes
 
be
 
hard
 
to
 
find
.

 
Perl's
 
function
 
documentation
 
remarks
 
on
 
the
 
variant
 
behavior
 
of
 
built-in
 
functions
 
in
 
list
 
and
 
scalar
 
contexts
 
that
 
"In
 
general
,

 
they
 
do
 
what
 
you
 
want
,

 
unless
 
you
 
want
 
consistency
.
"[26]


No
 
written
 
specification
 
or
 
standard
 
for
 
the
 
Perl
 
language
 
exists
 
for
 
Perl
 
versions
 
through
 
Perl
 
5
,

 
and
 
there
 
are
 
no
 
plans
 
to
 
create
 
one
 
for
 
the
 
current
 
version
 
of
 
Perl
.

 
There
 
has
 
been
 
only
 
one
 
implementation
 
of
 
the
 
interpreter
,

 
and
 
the
 
language
 
has
 
evolved
 
along
 
with
 
it
.

 
That
 
interpreter
,

 
together
 
with
 
its
 
functional
 
tests
,

 
stands
 
as
 
a
 
de
 
facto
 
specification
 
of
 
the
 
language
.

 
Perl
 
6
,

 
however
,

 
started
 
with
 
a
 
specification
,
[27]
 
and
 
several
 
projects[28]
 
aim
 
to
 
implement
 
some
 
or
 
all
 
of
 
the
 
specification
.






Applications


Perl
 
has
 
many
 
and
 
varied
 
applications
,

 
compounded
 
by
 
the
 
availability
 
of
 
many
 
standard
 
and
 
third-party
 
modules
.



Ever
 
since
 
the
 
early
 
days
 
of
 
the
 
Web
,

 
programmers
 
have
 
used
 
Perl
 
to
 
write
 
CGI
 
scripts
.

 
Perl
 
is
 
known
 
as
 
one
 
of
 
"the
 
three
 
Ps"
 
(along
 
with
 
Python
 
and
 
PHP)
,

 
the
 
most
 
popular
 
dynamic
 
languages
 
for
 
writing
 
Web
 
applications
.

 
It
 
is
 
also
 
an
 
integral
 
component
 
of
 
the
 
popular
 
LAMP
 
solution
 
stack
 
for
 
web
 
development
.

 
Large
 
projects
 
written
 
in
 
Perl
 
include
 
cPanel
,

 
Slash
,

 
Bugzilla
,

 
RT
,

 
TWiki
,

 
and
 
Movable
 
Type
.

 
Many
 
high-traffic
 
websites
 
use
 
Perl
 
extensively
.

 
Examples
 
include
 
Amazon
.
com
,

 
bbc
.
co
.
uk
,

 
Priceline
.
com
,

 
Craigslist
,
[29]
 
IMDb
,
[30]
 
LiveJournal
,

 
Slashdot
 
and
 
Ticketmaster
.



Perl
 
is
 
often
 
used
 
as
 
a
 
glue
 
language
,

 
tying
 
together
 
systems
 
and
 
interfaces
 
that
 
were
 
not
 
specifically
 
designed
 
to
 
interoperate
,

 
and
 
for
 
"data
 
munging"
,
[31]
 
that
 
is
,

 
converting
 
or
 
processing
 
large
 
amounts
 
of
 
data
 
for
 
tasks
 
such
 
as
 
creating
 
reports
.

 
In
 
fact
,

 
these
 
strengths
 
are
 
intimately
 
linked
.

 
The
 
combination
 
makes
 
Perl
 
a
 
popular
 
all-purpose
 
language
 
for
 
system
 
administrators
,

 
particularly
 
because
 
short
 
programs
 
can
 
be
 
entered
 
and
 
run
 
on
 
a
 
single
 
command
 
line
.



With
 
a
 
degree
 
of
 
care
,

 
Perl
 
code
 
can
 
be
 
made
 
portable
 
across
 
Windows
 
and
 
Unix
.

 
Portable
 
Perl
 
code
 
is
 
often
 
used
 
by
 
suppliers
 
of
 
software
 
(both
 
COTS
 
and
 
bespoke)
 
to
 
simplify
 
packaging
 
and
 
maintenance
 
of
 
software
 
build-
 
and
 
deployment-scripts
.



Graphical
 
user
 
interfaces
 
(GUIs)
 
may
 
be
 
developed
 
using
 
Perl
.

 
For
 
example
,

 
Perl
/
Tk
 
is
 
commonly
 
used
 
to
 
enable
 
user
 
interaction
 
with
 
Perl
 
scripts
.

 
Such
 
interaction
 
may
 
be
 
synchronous
 
or
 
asynchronous
,

 
using
 
callbacks
 
to
 
update
 
the
 
GUI
.

 
For
 
more
 
information
 
about
 
the
 
technologies
 
involved
,

 
see
 
Tk
,

 
Tcl
 
and
 
WxPerl
.



Perl
 
is
 
also
 
widely
 
used
 
in
 
finance
 
and
 
in
 
bioinformatics
,

 
where
 
it
 
is
 
valued
 
for
 
rapid
 
application
 
development
 
and
 
deployment
 
and
 
for
 
its
 
capability
 
to
 
handle
 
large
 
data-sets
.






Implementation


Perl
 
is
 
implemented
 
as
 
a
 
core
 
interpreter
,

 
written
 
in
 
C
,

 
together
 
with
 
a
 
large
 
collection
 
of
 
modules
,

 
written
 
in
 
Perl
 
and
 
C
.

 
As
 
of
 
2010
,

 
the
 
stable
 
version
 
(5
.
12
.
3)
 
is
 
14
.
2
 
MB
 
when
 
packaged
 
in
 
a
 
tar
 
file
 
and
 
gzip
 
compressed
.
[32]
 
The
 
interpreter
 
is
 
150
,
000
 
lines
 
of
 
C
 
code
 
and
 
compiles
 
to
 
a
 
1
 
MB
 
executable
 
on
 
typical
 
machine
 
architectures
.

 
Alternatively
,

 
the
 
interpreter
 
can
 
be
 
compiled
 
to
 
a
 
link
 
library
 
and
 
embedded
 
in
 
other
 
programs
.

 
There
 
are
 
nearly
 
500
 
modules
 
in
 
the
 
distribution
,

 
comprising
 
200
,
000
 
lines
 
of
 
Perl
 
and
 
an
 
additional
 
350
,
000
 
lines
 
of
 
C
 
code
.

 
(Much
 
of
 
the
 
C
 
code
 
in
 
the
 
modules
 
consists
 
of
 
character-encoding
 
tables
.
)


The
 
interpreter
 
has
 
an
 
object-oriented
 
architecture
.

 
All
 
of
 
the
 
elements
 
of
 
the
 
Perl
 
language—scalars
,

 
arrays
,

 
hashes
,

 
coderefs
,

 
filehandles—are
 
represented
 
in
 
the
 
interpreter
 
by
 
C
 
structs
.

 
Operations
 
on
 
these
 
structs
 
are
 
defined
 
by
 
a
 
large
 
collection
 
of
 
macros
,

 
typedefs
,

 
and
 
functions
;

 
these
 
constitute
 
the
 
Perl
 
C
 
API
.

 
The
 
Perl
 
API
 
can
 
be
 
bewildering
 
to
 
the
 
uninitiated
,

 
but
 
its
 
entry
 
points
 
follow
 
a
 
consistent
 
naming-scheme
,

 
which
 
provides
 
guidance
 
to
 
those
 
who
 
use
 
it
.



The
 
life
 
of
 
a
 
Perl
 
interpreter
 
divides
 
broadly
 
into
 
a
 
compile
 
phase
 
and
 
a
 
run
 
phase
.
[33]
 
In
 
Perl
,

 
the
 
phases
 
are
 
the
 
major
 
stages
 
in
 
the
 
interpreter's
 
life-cycle
.

 
Each
 
interpreter
 
goes
 
through
 
each
 
phase
 
only
 
once
,

 
and
 
the
 
phases
 
follow
 
in
 
a
 
fixed
 
sequence
.



Most
 
of
 
what
 
happens
 
in
 
Perl's
 
compile
 
phase
 
is
 
compilation
,

 
and
 
most
 
of
 
what
 
happens
 
in
 
Perl's
 
run
 
phase
 
is
 
execution
,

 
but
 
there
 
are
 
significant
 
exceptions
.

 
Perl
 
makes
 
important
 
use
 
of
 
its
 
capability
 
to
 
execute
 
Perl
 
code
 
during
 
the
 
compile
 
phase
.

 
Perl
 
will
 
also
 
delay
 
compilation
 
into
 
the
 
run
 
phase
.

 
The
 
terms
 
that
 
indicate
 
the
 
kind
 
of
 
processing
 
that
 
is
 
actually
 
occurring
 
at
 
any
 
moment
 
are
 
compile
 
time
 
and
 
run
 
time
.

 
Perl
 
is
 
in
 
compile
 
time
 
at
 
most
 
points
 
during
 
the
 
compile
 
phase
,

 
but
 
compile
 
time
 
may
 
also
 
be
 
entered
 
during
 
the
 
run
 
phase
.

 
The
 
compile
 
time
 
for
 
code
 
in
 
a
 
string
 
argument
 
passed
 
to
 
the
 
eval
 
built-in
 
occurs
 
during
 
the
 
run
 
phase
.

 
Perl
 
is
 
often
 
in
 
run
 
time
 
during
 
the
 
compile
 
phase
 
and
 
spends
 
most
 
of
 
the
 
run
 
phase
 
in
 
run
 
time
.

 
Code
 
in
 
BEGIN
 
blocks
 
executes
 
at
 
run
 
time
 
but
 
in
 
the
 
compile
 
phase
.



At
 
compile
 
time
,

 
the
 
interpreter
 
parses
 
Perl
 
code
 
into
 
a
 
syntax
 
tree
.

 
At
 
run
 
time
,

 
it
 
executes
 
the
 
program
 
by
 
walking
 
the
 
tree
.

 
Text
 
is
 
parsed
 
only
 
once
,

 
and
 
the
 
syntax
 
tree
 
is
 
subject
 
to
 
optimization
 
before
 
it
 
is
 
executed
,

 
so
 
that
 
execution
 
is
 
relatively
 
efficient
.

 
Compile-time
 
optimizations
 
on
 
the
 
syntax
 
tree
 
include
 
constant
 
folding
 
and
 
context
 
propagation
,

 
but
 
peephole
 
optimization
 
is
 
also
 
performed
.



Perl
 
has
 
a
 
Turing-complete
 
grammar
 
because
 
parsing
 
can
 
be
 
affected
 
by
 
run-time
 
code
 
executed
 
during
 
the
 
compile
 
phase
.
[34]
 
Therefore
,

 
Perl
 
cannot
 
be
 
parsed
 
by
 
a
 
straight
 
Lex
/
Yacc
 
lexer
/
parser
 
combination
.

 
Instead
,

 
the
 
interpreter
 
implements
 
its
 
own
 
lexer
,

 
which
 
coordinates
 
with
 
a
 
modified
 
GNU
 
bison
 
parser
 
to
 
resolve
 
ambiguities
 
in
 
the
 
language
.



It
 
is
 
often
 
said
 
that
 
"Only
 
perl
 
can
 
parse
 
Perl"
,
[35]
 
meaning
 
that
 
only
 
the
 
Perl
 
interpreter
 
(perl)
 
can
 
parse
 
the
 
Perl
 
language
 
(Perl)
,

 
but
 
even
 
this
 
is
 
not
,

 
in
 
general
,

 
true
.

 
Because
 
the
 
Perl
 
interpreter
 
can
 
simulate
 
a
 
Turing
 
machine
 
during
 
its
 
compile
 
phase
,

 
it
 
would
 
need
 
to
 
decide
 
the
 
Halting
 
Problem
 
in
 
order
 
to
 
complete
 
parsing
 
in
 
every
 
case
.

 
It's
 
a
 
long-standing
 
result
 
that
 
the
 
Halting
 
Problem
 
is
 
undecidable
,

 
and
 
therefore
 
not
 
even
 
perl
 
can
 
always
 
parse
 
Perl
.

 
Perl
 
makes
 
the
 
unusual
 
choice
 
of
 
giving
 
the
 
user
 
access
 
to
 
its
 
full
 
programming
 
power
 
in
 
its
 
own
 
compile
 
phase
.

 
The
 
cost
 
in
 
terms
 
of
 
theoretical
 
purity
 
is
 
high
,

 
but
 
practical
 
inconvenience
 
seems
 
to
 
be
 
rare
.



Other
 
programs
 
that
 
undertake
 
to
 
parse
 
Perl
,

 
such
 
as
 
source-code
 
analyzers
 
and
 
auto-indenters
,

 
have
 
to
 
contend
 
not
 
only
 
with
 
ambiguous
 
syntactic
 
constructs
 
but
 
also
 
with
 
the
 
undecidability
 
of
 
Perl
 
parsing
 
in
 
the
 
general
 
case
.

 
Adam
 
Kennedy's
 
PPI
 
project
 
focused
 
on
 
parsing
 
Perl
 
code
 
as
 
a
 
document
 
(retaining
 
its
 
integrity
 
as
 
a
 
document)
,

 
instead
 
of
 
parsing
 
Perl
 
as
 
executable
 
code
 
(which
 
not
 
even
 
Perl
 
itself
 
can
 
always
 
do)
.

 
It
 
was
 
Kennedy
 
who
 
first
 
conjectured
 
that
 
"parsing
 
Perl
 
suffers
 
from
 
the
 
'Halting
 
Problem'"
,
[36]
 
which
 
was
 
later
 
proved
.
[37]


Perl
 
is
 
distributed
 
with
 
some
 
120
,
000
 
functional
 
tests
.

 
These
 
run
 
as
 
part
 
of
 
the
 
normal
 
build
 
process
 
and
 
extensively
 
exercise
 
the
 
interpreter
 
and
 
its
 
core
 
modules
.

 
Perl
 
developers
 
rely
 
on
 
the
 
functional
 
tests
 
to
 
ensure
 
that
 
changes
 
to
 
the
 
interpreter
 
do
 
not
 
introduce
 
bugs
;

 
additionally
,

 
Perl
 
users
 
who
 
see
 
that
 
the
 
interpreter
 
passes
 
its
 
functional
 
tests
 
on
 
their
 
system
 
can
 
have
 
a
 
high
 
degree
 
of
 
confidence
 
that
 
it
 
is
 
working
 
properly
.



Maintenance
 
of
 
the
 
Perl
 
interpreter
 
has
 
become
 
increasingly
 
difficult
 
over
 
the
 
years
.

 
The
 
code
 
base
 
has
 
undergone
 
continuous
 
development
 
since
 
1994
.

 
The
 
code
 
has
 
been
 
optimized
 
for
 
performance
 
at
 
the
 
expense
 
of
 
simplicity
,

 
clarity
,

 
and
 
strong
 
internal
 
interfaces
.

 
New
 
features
 
have
 
been
 
added
,

 
yet
 
virtually
 
complete
 
backward
 
compatibility
 
with
 
earlier
 
versions
 
is
 
maintained
.

 
Major
 
releases
 
of
 
Perl
 
were
 
coordinated
 
by
 
Perl
 
pumpkings
,
[38]
 
which
 
handled
 
integrating
 
patch
 
submissions
 
and
 
bug
 
fixes
,

 
but
 
the
 
language
 
has
 
since
 
changed
 
to
 
a
 
rotating
,

 
monthly
 
release
 
cycle
.

 
Development
 
discussion
 
takes
 
place
 
via
 
the
 
perl5_porters
 
mailing
 
list
.

 
As
 
of
 
Perl
 
5
.
11
,

 
development
 
efforts
 
have
 
included
 
refactoring
 
certain
 
core
 
modules
 
known
 
as
 
'dual
 
lifed'
 
modules
 
out
 
of
 
the
 
Perl
 
core[39]
 
to
 
help
 
alleviate
 
some
 
of
 
these
 
problems
.



[edit]Availability


Perl
 
is
 
dual
 
licensed
 
under
 
both
 
the
 
Artistic
 
License
 
and
 
the
 
GNU
 
General
 
Public
 
License
.

 
Distributions
 
are
 
available
 
for
 
most
 
operating
 
systems
.

 
It
 
is
 
particularly
 
prevalent
 
on
 
Unix
 
and
 
Unix-like
 
systems
,

 
but
 
it
 
has
 
been
 
ported
 
to
 
most
 
modern
 
(and
 
many
 
obsolete)
 
platforms
.

 
With
 
only
 
six
 
reported
 
exceptions
,

 
Perl
 
can
 
be
 
compiled
 
from
 
source
 
code
 
on
 
all
 
POSIX-compliant
,

 
or
 
otherwise-Unix-compatible
 
platforms
.
[40]


Because
 
of
 
unusual
 
changes
 
required
 
for
 
the
 
Mac
 
OS
 
Classic
 
environment
,

 
a
 
special
 
port
 
called
 
MacPerl
 
was
 
shipped
 
independently
.
[41]


The
 
Comprehensive
 
Perl
 
Archive
 
Network
 
carries
 
a
 
complete
 
list
 
of
 
supported
 
platforms
 
with
 
links
 
to
 
the
 
distributions
 
available
 
on
 
each
.
[42]
 
CPAN
 
is
 
also
 
the
 
source
 
for
 
publicly
 
available
 
Perl
 
modules
 
that
 
are
 
not
 
part
 
of
 
the
 
core
 
Perl
 
distribution
.



[edit]Windows


Users
 
of
 
Microsoft
 
Windows
 
typically
 
install
 
one
 
of
 
the
 
native
 
binary
 
distributions
 
of
 
Perl
 
for
 
Win32
,

 
most
 
commonly
 
Strawberry
 
Perl
 
or
 
ActivePerl
.

 
Compiling
 
Perl
 
from
 
source
 
code
 
under
 
Windows
 
is
 
possible
,

 
but
 
most
 
installations
 
lack
 
the
 
requisite
 
C
 
compiler
 
and
 
build
 
tools
.

 
This
 
also
 
makes
 
it
 
difficult
 
to
 
install
 
modules
 
from
 
the
 
CPAN
,

 
particularly
 
those
 
that
 
are
 
partially
 
written
 
in
 
C
.



ActivePerl
 
is
 
a
 
closed
 
source
 
distribution
 
from
 
ActiveState
 
that
 
has
 
regular
 
releases
 
that
 
track
 
the
 
core
 
Perl
 
releases
.
[43]
 
The
 
distribution
 
also
 
includes
 
the
 
Perl
 
package
 
manager
 
(PPM)
,
[44]
 
a
 
popular
 
tool
 
for
 
installing
,

 
removing
,

 
upgrading
,

 
and
 
managing
 
the
 
use
 
of
 
common
 
Perl
 
modules
.



Strawberry
 
Perl
 
is
 
an
 
open
 
source
 
distribution
 
for
 
Windows
.

 
It
 
has
 
had
 
regular
,

 
quarterly
 
releases
 
since
 
January
 
2008
,

 
including
 
new
 
modules
 
as
 
feedback
 
and
 
requests
 
come
 
in
.

 
Strawberry
 
Perl
 
aims
 
to
 
be
 
able
 
to
 
install
 
modules
 
like
 
standard
 
Perl
 
distributions
 
on
 
other
 
platforms
,

 
including
 
compiling
 
XS
 
modules
.



The
 
Cygwin
 
emulation
 
layer
 
is
 
another
 
way
 
of
 
running
 
Perl
 
under
 
Windows
.

 
Cygwin
 
provides
 
a
 
Unix-like
 
environment
 
on
 
Windows
,

 
and
 
both
 
Perl
 
and
 
CPAN
 
are
 
available
 
as
 
standard
 
pre-compiled
 
packages
 
in
 
the
 
Cygwin
 
setup
 
program
.

 
Because
 
Cygwin
 
also
 
includes
 
the
 
gcc
,

 
compiling
 
Perl
 
from
 
source
 
is
 
also
 
possible
.



[edit]Database
 
interfaces





Perl
 
is
 
widely
 
favored
 
for
 
database
 
applications
.

 
Its
 
text-handling
 
facilities
 
are
 
useful
 
for
 
generating
 
SQL
 
queries
;

 
arrays
,

 
hashes
,

 
and
 
automatic
 
memory
 
management
 
make
 
it
 
easy
 
to
 
collect
 
and
 
process
 
the
 
returned
 
data
.



In
 
early
 
versions
 
of
 
Perl
,

 
database
 
interfaces
 
were
 
created
 
by
 
relinking
 
the
 
interpreter
 
with
 
a
 
client-side
 
database
 
library
.

 
This
 
was
 
sufficiently
 
difficult
 
that
 
it
 
was
 
done
 
for
 
only
 
a
 
few
 
of
 
the
 
most-important
 
and
 
most
 
widely
 
used
 
databases
,

 
and
 
it
 
restricted
 
the
 
resulting
 
perl
 
executable
 
to
 
using
 
just
 
one
 
database
 
interface
 
at
 
a
 
time
.



In
 
Perl
 
5
,

 
database
 
interfaces
 
are
 
implemented
 
by
 
Perl
 
DBI
 
modules
.

 
The
 
DBI
 
(Database
 
Interface)
 
module
 
presents
 
a
 
single
,

 
database-independent
 
interface
 
to
 
Perl
 
applications
,

 
while
 
the
 
DBD
 
(Database
 
Driver)
 
modules
 
handle
 
the
 
details
 
of
 
accessing
 
some
 
50
 
different
 
databases
;

 
there
 
are
 
DBD
 
drivers
 
for
 
most
 
ANSI
 
SQL
 
databases
.



DBI
 
provides
 
caching
 
for
 
database
 
handles
 
and
 
queries
,

 
which
 
can
 
greatly
 
improve
 
performance
 
in
 
long-lived
 
execution
 
environments
 
such
 
as
 
mod_perl
,
[45]
 
helping
 
high-volume
 
systems
 
avert
 
load
 
spikes
 
as
 
in
 
the
 
Slashdot
 
effect
.



In
 
modern
 
Perl
 
applications
,

 
especially
 
those
 
written
 
using
 
Web
 
application
 
frameworks
 
such
 
as
 
Catalyst
,

 
the
 
DBI
 
module
 
is
 
often
 
used
 
indirectly
 
via
 
object-relational
 
mappers
 
such
 
as
 
DBIx::Class
,

 
Class::DBI
 
or
 
Rose::DB::Object
 
which
 
generate
 
SQL
 
queries
 
and
 
handle
 
data
 
transparently
 
to
 
the
 
application
 
author
.



[edit]Comparative
 
performance





The
 
Computer
 
Language
 
Benchmarks
 
Game
,

 
a
 
project
 
hosted
 
by
 
Alioth
,

 
compares
 
the
 
performance
 
of
 
implementations
 
of
 
typical
 
programming
 
problems
 
in
 
several
 
programming
 
languages
.
[46]
 
The
 
submitted
 
Perl
 
implementations
 
typically
 
perform
 
toward
 
the
 
high
 
end
 
of
 
the
 
memory-usage
 
spectrum
 
and
 
give
 
varied
 
speed
 
results
.

 
Perl's
 
performance
 
in
 
the
 
benchmarks
 
game
 
is
 
typical
 
for
 
interpreted
 
languages
.
[47]


Large
 
Perl
 
programs
 
start
 
more
 
slowly
 
than
 
similar
 
programs
 
in
 
compiled
 
languages
 
because
 
perl
 
has
 
to
 
compile
 
the
 
source
 
every
 
time
 
it
 
runs
.

 
In
 
a
 
talk
 
at
 
the
 
YAPC::Europe
 
2005
 
conference
 
and
 
subsequent
 
article
 
"A
 
Timely
 
Start"
,

 
Jean-Louis
 
Leroy
 
found
 
that
 
his
 
Perl
 
programs
 
took
 
much
 
longer
 
to
 
run
 
than
 
he
 
expected
 
because
 
the
 
perl
 
interpreter
 
spent
 
much
 
of
 
the
 
time
 
finding
 
modules
 
because
 
of
 
his
 
over-large
 
include
 
path
.
[48]
 
Unlike
 
Java
,

 
Python
,

 
and
 
Ruby
,

 
Perl
 
has
 
only
 
experimental
 
support
 
for
 
pre-compiling
.
[49]
 
Therefore
 
Perl
 
programs
 
pay
 
this
 
overhead
 
penalty
 
on
 
every
 
execution
.

 
The
 
run
 
phase
 
of
 
typical
 
programs
 
is
 
long
 
enough
 
that
 
amortized
 
startup
 
time
 
is
 
not
 
substantial
,

 
but
 
benchmarks
 
that
 
measure
 
very
 
short
 
execution
 
times
 
are
 
likely
 
to
 
be
 
skewed
 
due
 
to
 
this
 
overhead
.



A
 
number
 
of
 
tools
 
have
 
been
 
introduced
 
to
 
improve
 
this
 
situation
.

 
The
 
first
 
such
 
tool
 
was
 
Apache's
 
mod_perl
,

 
which
 
sought
 
to
 
address
 
one
 
of
 
the
 
most-common
 
reasons
 
that
 
small
 
Perl
 
programs
 
were
 
invoked
 
rapidly:
 
CGI
 
Web
 
development
.

 
ActivePerl
,

 
via
 
Microsoft
 
ISAPI
,

 
provides
 
similar
 
performance
 
improvements
.



Once
 
Perl
 
code
 
is
 
compiled
,

 
there
 
is
 
additional
 
overhead
 
during
 
the
 
execution
 
phase
 
that
 
typically
 
isn't
 
present
 
for
 
programs
 
written
 
in
 
compiled
 
languages
 
such
 
as
 
C
 
or
 
C
+

+

.

 
Examples
 
of
 
such
 
overhead
 
include
 
bytecode
 
interpretation
,

 
reference-counting
 
memory
 
management
,

 
and
 
dynamic
 
type-checking
.



[edit]Optimizing


Like
 
any
 
code
,

 
Perl
 
programs
 
can
 
be
 
tuned
 
for
 
performance
 
using
 
benchmarks
 
and
 
profiles
 
after
 
a
 
readable
 
and
 
correct
 
implementation
 
is
 
finished
.

 
In
 
part
 
because
 
of
 
Perl's
 
interpreted
 
nature
,

 
writing
 
more-efficient
 
Perl
 
will
 
not
 
always
 
be
 
enough
 
to
 
meet
 
one's
 
performance
 
goals
 
for
 
a
 
program
.



In
 
such
 
situations
,

 
the
 
most-critical
 
routines
 
of
 
a
 
Perl
 
program
 
can
 
be
 
written
 
in
 
other
 
languages
 
such
 
as
 
C
 
or
 
Assembler
,

 
which
 
can
 
be
 
connected
 
to
 
Perl
 
via
 
simple
 
Inline
 
modules
 
or
 
the
 
more-complex-but-flexible
 
XS
 
mechanism
.
[50]
 
Nicholas
 
Clark
,

 
a
 
Perl
 
core
 
developer
,

 
discusses
 
some
 
Perl
 
design
 
trade-offs
 
and
 
solutions
 
in
 
a
 
2002
 
document
 
called
 
"When
 
perl
 
is
 
not
 
quite
 
fast
 
enough"
.
[51]





At
 
the
 
2000
 
Perl
 
Conference
,

 
Jon
 
Orwant
 
made
 
a
 
case
 
for
 
a
 
major
 
new
 
language
 
initiative
.
[53]
 
This
 
led
 
to
 
a
 
decision
 
to
 
begin
 
work
 
on
 
a
 
redesign
 
of
 
the
 
language
,

 
to
 
be
 
called
 
Perl
 
6
.

 
Proposals
 
for
 
new
 
language
 
features
 
were
 
solicited
 
from
 
the
 
Perl
 
community
 
at
 
large
,

 
and
 
more
 
than
 
300
 
RFCs
 
were
 
submitted
.



Larry
 
Wall
 
spent
 
the
 
next
 
few
 
years
 
digesting
 
the
 
RFCs
 
and
 
synthesizing
 
them
 
into
 
a
 
coherent
 
framework
 
for
 
Perl
 
6
.

 
He
 
has
 
presented
 
his
 
design
 
for
 
Perl
 
6
 
in
 
a
 
series
 
of
 
documents
 
called
 
"apocalypses"
,

 
which
 
are
 
numbered
 
to
 
correspond
 
to
 
chapters
 
in
 
Programming
 
Perl
.

 
As
 
of
 
January
 
2011
,

 
the
 
developing
 
specification
 
of
 
Perl
 
6
 
is
 
encapsulated
 
in
 
design
 
documents
 
called
 
Synopses
,

 
which
 
are
 
numbered
 
to
 
correspond
 
to
 
Apocalypses
.
[54]


Perl
 
6
 
is
 
not
 
intended
 
to
 
be
 
backward
 
compatible
,

 
although
 
there
 
will
 
be
 
a
 
compatibility
 
mode
.

 
Perl
 
6
 
and
 
Perl
 
5
 
are
 
distinct
 
languages
 
with
 
a
 
common
 
ancestry
.
[55]


Thesis
 
work
 
by
 
Bradley
 
M
.

 
Kuhn
,

 
overseen
 
by
 
Larry
 
Wall
,

 
considered
 
the
 
possible
 
use
 
of
 
the
 
Java
 
virtual
 
machine
 
as
 
a
 
runtime
 
for
 
Perl
.
[56]
 
Kuhn's
 
thesis
 
showed
 
this
 
approach
 
to
 
be
 
problematic
.

 
In
 
2001
,

 
it
 
was
 
decided
 
that
 
Perl
 
6
 
would
 
run
 
on
 
a
 
cross-language
 
virtual
 
machine
 
called
 
Parrot
.

 
This
 
will
 
mean
 
that
 
other
 
languages
 
targeting
 
the
 
Parrot
 
will
 
gain
 
native
 
access
 
to
 
CPAN
,

 
allowing
 
some
 
level
 
of
 
cross-language
 
development
.



In
 
2005
,

 
Audrey
 
Tang
 
created
 
the
 
pugs
 
project
,

 
an
 
implementation
 
of
 
Perl
 
6
 
in
 
Haskell
.

 
This
 
was
,

 
and
 
continues
 
to
 
act
 
as
,

 
a
 
test
 
platform
 
for
 
the
 
Perl
 
6
 
language
 
(separate
 
from
 
the
 
development
 
of
 
the
 
actual
 
implementation)
 
allowing
 
the
 
language
 
designers
 
to
 
explore
.

 
The
 
pugs
 
project
 
spawned
 
an
 
active
 
Perl
/
Haskell
 
cross-language
 
community
 
centered
 
around
 
the
 
freenode
 
#perl6
 
IRC
 
channel
.



A
 
number
 
of
 
features
 
in
 
the
 
Perl
 
6
 
language
 
now
 
show
 
similarities
 
to
 
Haskell
.
[citation
 
needed]


As
 
of
 
2012
,

 
Perl
 
6
 
development
 
is
 
primarily
 
centered
 
around
 
two
 
compilers[57]
,

 
Rakudo
 
Perl
 
6
,

 
an
 
implementation
 
running
 
on
 
top
 
of
 
the
 
Parrot
 
virtual
 
machine
,

 
and
 
Niecza
,

 
which
 
targets
 
the
 
Common
 
Language
 
Runtime
.



[edit]Future
 
of
 
Perl
 
5





Development
 
of
 
Perl
 
5
 
is
 
also
 
continuing
.

 
Perl
 
5
.
12
.
0
 
was
 
released
 
in
 
April
 
2010
 
with
 
some
 
new
 
features
 
influenced
 
by
 
the
 
design
 
of
 
Perl
 
6
.
[10][58]
 
Perl
 
5
.
14
.
1
 
was
 
released
 
on
 
June
 
17
,

 
2011
.

 
Perl
 
5
 
development
 
versions
 
are
 
released
 
on
 
a
 
monthly
 
basis
,

 
with
 
major
 
releases
 
coming
 
out
 
once
 
per
 
year
.
[59]


Future
 
plans
 
for
 
Perl
 
5
 
include
 
making
 
the
 
core
 
language
 
easier
 
to
 
extend
 
from
 
modules
,

 
and
 
providing
 
a
 
small
,

 
extensible
 
Meta-object
 
protocol
 
in
 
core
.
[60]


The
 
relative
 
proportion
 
of
 
searches
 
for
 
'Perl
 
programming'
,

 
as
 
compared
 
with
 
similar
 
searches
 
for
 
other
 
programming
 
languages
,

 
declined
 
from
 
2005
 
to
 
early
 
2011
 
(with
 
a
 
subsequent
 
increase
 
since
 
then)
.
[61]
 
However
,

 
according
 
to
 
this
 
same
 
source
,

 
Perl
 
has
 
been
 
one
 
of
 
the
 
top
 
ten
 
most
 
popular
 
programming
 
languages
 
since
 
records
 
began
 
in
 
2001
.
[62]


[edit]Perl
 
community





Perl's
 
culture
 
and
 
community
 
has
 
developed
 
alongside
 
the
 
language
 
itself
.

 
Usenet
 
was
 
the
 
first
 
public
 
venue
 
in
 
which
 
Perl
 
was
 
introduced
,

 
but
 
over
 
the
 
course
 
of
 
its
 
evolution
,

 
Perl's
 
community
 
was
 
shaped
 
by
 
the
 
growth
 
of
 
broadening
 
Internet-based
 
services
 
including
 
the
 
introduction
 
of
 
the
 
World
 
Wide
 
Web
.

 
The
 
community
 
that
 
surrounds
 
Perl
 
was
,

 
in
 
fact
,

 
the
 
topic
 
of
 
Larry
 
Wall's
 
first
 
"State
 
of
 
the
 
Onion"
 
talk
.
[63]


[edit]State
 
of
 
the
 
Onion


State
 
of
 
the
 
Onion
 
is
 
the
 
name
 
for
 
Larry
 
Wall’s
 
yearly
 
keynote-style
 
summaries
 
on
 
the
 
progress
 
of
 
Perl
 
and
 
its
 
community
.

 
They
 
are
 
characterized
 
by
 
his
 
hallmark
 
humor
,

 
employing
 
references
 
to
 
Perl’s
 
culture
,

 
the
 
wider
 
hacker
 
culture
,

 
Wall’s
 
linguistic
 
background
,

 
sometimes
 
his
 
family
 
life
,

 
and
 
occasionally
 
even
 
his
 
Christian
 
background
.



Each
 
talk
 
is
 
first
 
given
 
at
 
various
 
Perl
 
conferences
 
and
 
is
 
eventually
 
also
 
published
 
online
.



[edit]Perl
 
pastimes


JAPHs


In
 
email
,

 
Usenet
,

 
and
 
message
 
board
 
postings
,

 
"Just
 
another
 
Perl
 
hacker"
 
(JAPH)
 
programs
 
are
 
a
 
common
 
trend
,

 
originated
 
by
 
Randal
 
L
.

 
Schwartz
,

 
one
 
of
 
the
 
earliest
 
professional
 
Perl
 
trainers
.
[64]
 
In
 
the
 
parlance
 
of
 
Perl
 
culture
,

 
Perl
 
programmers
 
are
 
known
 
as
 
Perl
 
hackers
,

 
and
 
from
 
this
 
derives
 
the
 
practice
 
of
 
writing
 
short
 
programs
 
to
 
print
 
out
 
the
 
phrase
 
"Just
 
another
 
Perl
 
hacker
,
"
.

 
In
 
the
 
spirit
 
of
 
the
 
original
 
concept
,

 
these
 
programs
 
are
 
moderately
 
obfuscated
 
and
 
short
 
enough
 
to
 
fit
 
into
 
the
 
signature
 
of
 
an
 
email
 
or
 
Usenet
 
message
.

 
The
 
"canonical"
 
JAPH
 
as
 
developed
 
by
 
Schwartz
 
includes
 
the
 
comma
 
at
 
the
 
end
,

 
although
 
this
 
is
 
often
 
omitted
.
[65]


Perl
 
golf


Perl
 
"golf"
 
is
 
the
 
pastime
 
of
 
reducing
 
the
 
number
 
of
 
characters
 
(key
 
"strokes")
 
used
 
in
 
a
 
Perl
 
program
 
to
 
the
 
bare
 
minimum
,

 
much
 
as
 
how
 
golf
 
players
 
seek
 
to
 
take
 
as
 
few
 
shots
 
as
 
possible
 
in
 
a
 
round
.

 
The
 
phrase's
 
first
 
use
 
[66]
 
emphasized
 
the
 
difference
 
between
 
pedestrian
 
code
 
meant
 
to
 
teach
 
a
 
newcomer
 
and
 
terse
 
hacks
 
likely
 
to
 
amuse
 
experienced
 
Perl
 
programmers
,

 
an
 
example
 
of
 
the
 
latter
 
being
 
JAPHs
 
that
 
were
 
already
 
used
 
in
 
signatures
 
in
 
Usenet
 
postings
 
and
 
elsewhere
.

 
Similar
 
stunts
 
had
 
been
 
an
 
unnamed
 
pastime
 
in
 
the
 
language
 
APL
 
in
 
previous
 
decades
.

 
The
 
use
 
of
 
Perl
 
to
 
write
 
a
 
program
 
that
 
performed
 
RSA
 
encryption
 
prompted
 
a
 
widespread
 
and
 
practical
 
interest
 
in
 
this
 
pastime
.
[67]
 
In
 
subsequent
 
years
,

 
the
 
term
 
"code
 
golf"
 
has
 
been
 
applied
 
to
 
the
 
pastime
 
in
 
other
 
languages
.
[68]
 
A
 
Perl
 
Golf
 
Apocalypse
 
was
 
held
 
at
 
Perl
 
Conference
 
4
.
0
 
in
 
Monterey
,

 
California
 
in
 
July
 
2000
.



Obfuscation


As
 
with
 
C
,

 
obfuscated
 
code
 
competitions
 
were
 
a
 
well
 
known
 
pastime
 
in
 
the
 
late
 
1990s
.

 
The
 
Obfuscated
 
Perl
 
Contest
 
was
 
a
 
competition
 
held
 
by
 
The
 
Perl
 
Journal
 
from
 
1996
 
to
 
2000
 
that
 
made
 
an
 
arch
 
virtue
 
of
 
Perl's
 
syntactic
 
flexibility
.

 
Awards
 
were
 
given
 
for
 
categories
 
such
 
as
 
"most
 
powerful"—programs
 
that
 
made
 
efficient
 
use
 
of
 
space—and
 
"best
 
four-line
 
signature"
 
for
 
programs
 
that
 
fit
 
into
 
four
 
lines
 
of
 
76
 
characters
 
in
 
the
 
style
 
of
 
a
 
Usenet
 
signature
 
block
.
[69]


Poetry


Perl
 
poetry
 
is
 
the
 
practice
 
of
 
writing
 
poems
 
that
 
can
 
be
 
compiled
 
as
 
legal
 
Perl
 
code
,

 
for
 
example
 
the
 
piece
 
known
 
as
 
Black
 
Perl
.

 
This
 
hobby
 
is
 
made
 
possible
 
by
 
the
 
large
 
number
 
of
 
English
 
words
 
that
 
are
 
used
 
in
 
the
 
Perl
.

 
New
 
poems
 
are
 
regularly
 
submitted
 
to
 
the
 
community
 
at
 
PerlMonks
.
[70]





CPAN
 
Acme


There
 
are
 
also
 
many
 
examples
 
of
 
code
 
written
 
purely
 
for
 
entertainment
 
on
 
the
 
CPAN
.

 
Lingua::Romana::Perligata
,

 
for
 
example
,

 
allows
 
writing
 
programs
 
in
 
Latin
.
[71]
 
Upon
 
execution
 
of
 
such
 
a
 
program
,

 
the
 
module
 
translates
 
its
 
source
 
code
 
into
 
regular
 
Perl
 
and
 
runs
 
it
.



The
 
Perl
 
community
 
has
 
set
 
aside
 
the
 
"Acme"
 
namespace
 
for
 
modules
 
that
 
are
 
fun
 
in
 
nature
 
(but
 
its
 
scope
 
has
 
widened
 
to
 
include
 
exploratory
 
or
 
experimental
 
code
 
or
 
any
 
other
 
module
 
that
 
is
 
not
 
meant
 
to
 
ever
 
be
 
used
 
in
 
production)
.

 
Some
 
of
 
the
 
Acme
 
modules
 
are
 
deliberately
 
implemented
 
in
 
amusing
 
ways
.

 
This
 
includes
 
Acme::Bleach
,

 
one
 
of
 
the
 
first
 
modules
 
in
 
the
 
Acme::
 
namespace
,
[72]
 
which
 
allows
 
the
 
program's
 
source
 
code
 
to
 
be
 
"whitened"
 
(i
.
e
.

,

 
all
 
characters
 
replaced
 
with
 
whitespace)
 
and
 
yet
 
still
 
work
.