Not sitting at an XP box, but an XP user may be able to augment this.

This sounds like an XP association's issue, which, if diddling the registry sounds like more of a challenge than you wish to confront, you may be able to deal with this way:

In the file manager, there's an Option for File associations. There (sorry, I may have missed one level here) you should be able to edit the associations... and you'll have to be careful to create a new run or open association with your AS Perl installation.

Be careful. Depending on how you work, you may have (or, "need") an association for edit.