I've noticed this issue after wanting to log the output of configure as ./configure (...) 2>&1 | tee configure.log
All following configure commands issued a weird syntax error.
All files named configure.* in the root directory are sourced regardless of the extension (.log, .txt. .bak)...
In the case of a configure.bak, you enter an infinite loop, in most other cases (*log) spurious error messages.