As another monk mentioned the .plx is an Activestate extension for PerlScript code that will be run off of an IIS web server (or rather more accurately an ISAPI enabled web server). Contrary to assertions made by some monks perl extensions do have meaning and the pervailing conventions shouldn't be ignored. For instance a .plx file shouldn't contain exec() as it isnt supported by the PerlScript engine. For CPAN authors using .perl (or other non .pl variants)instead of .pl is a bad idea as .pl scripts will get installed automatically in the perl/bin directory when doing a make install and their personal favorite wont. At least not without annoying modification of their makefile.pl (or maybe their build.pl), which in of itself shouldn't be renamed or the automated systems in CPAN.pm or CPANPlus.pm will break.

Theres another, totally aesthetic reason for complying with convention. For OS's that support associating icons to extensions it means that all of the various types are visually differentiable. For instance on my system all of the different common extensions have an icon associated. .pl files have the old style ActiveState yellow pearl, .pm have a nice dark blue pearl, and .t files have a nice green one. So if I download your conventionally named files ill readily identify them and their type by icon, the oddball variants wont be so easily distinguished. So id say stick with the conventional names unless you have a really good justification for doing so.