the 'diff' subroutine is in the file diff.pm. This module has to be in one of your include directories. Try this:

perl -d diff.pl file1 file2
...
DB<1> x @INC
0  'C:/Perl/lib'
1  'C:/Perl/site/lib'
2  '.'
DB<2>q
[download]

This will show you what your include directories are. diff.pm has to be in one of them.

Oryx3