If you're talking about sharing with other monks "hacks" to improve/customize the way the site actually looks/works for you, then I'd post those in Perl Monks Discussion. This would be similar to the collection of "Free Nodelet Hacks" which some monks have posted over time. Those are specifically about what we can do with the Free Nodelet, including JS. There have also been some CSS posts similarly, though without a nice unifying title tag which would make them easier to find as a "collection". If you SS for CSS, most of the hits will be relevant.
If you're talking about perl code which really runs in/on the client, then I would post that in Cool Uses for Perl, and include an appropriate keyword in the title, i.e. "perlmonks". There have been numerous posts like that over the years, which you'll find if you SS for "monks" in CUFP, Craft, Code, and Snippets. (In fact, CodeCatacombs has a "category" for PerlMonks Related Scripts, which is probably a lot like what you're talking about. But all those code sections have been deprecated in favor of CUFP, which does not have categories; you have to put keywords in the title field.)
I reckon we are the only monastery ever to have a dungeon stuffed with 16
,000 zombies.