Modifier highlighting fails if only one modifier name with a variable

[wwalker]

First, Thank you for writing i3-config.vim!

Not an important issues, but sometimes vim doesn't highlight the modifier keywords.

# vim: ft=i3config
# These lines do NOT syntax highlight the Control, Shift, or Alt:

bindsym Control+$mod+m unmark x
bindsym Shift+$mod+m unmark x
bindsym Alt+$mod+m unmark x

bindsym Control+$alt+m unmark x
bindsym Shift+$alt+m unmark x
bindsym Alt+$alt+m unmark x

# These lines DO syntax highlight the Control, Shift, or Alt:
bindsym Control+m unmark x
bindsym Shift+m unmark x
bindsym Alt+m unmark x

bindsym Shift+Control+$mod+m unmark x
bindsym Alt+Shift+$mod+m unmark x
bindsym Shift+Alt+$mod+m unmark x

[wwalker]

[mboughaba]

Will look into it thanks for the report !!!