No, your theory was correct. 1.1901 was the version installed with cygwin Perl which wasn't the Perl giving the error. PPM gets you version 1.15 which the original querent was eventually able to see was the problem (via the chatterbox).

Since the original question mentions XP, it would have helped had you used Win32-style quoting in your suggestion of how to report the module version number:

perl -MAlgorithm::Diff -e"print $Algorithm::Diff::VE­RSION"
[download]

or, since Algorithm::Diff uses Exporter.pm, just:

perl -MAlgorithm::Diff=9999 -e0
[download]

(FYI)

Thanks for the quick response with an excellent guess (which even turned out to be correct).