There's a good chance you have a path mismatch between Cygwin and AS Perl. When you start Cygwin, you'll rarely be in the directory you were in when you ran cygwin.bat to get into the environment.

If you fix the error in your code that ikegami pointed out, you might find out this is what pointed out your bug to you. This is a good example of why code that is more portable is more likely to be correct.