Remove Perl5 support

This was originally added to keep feature parity with purple2, but it has been
a huge pain, there's no solution on macOS, it randomly breaks, and there never
really was a lot of adoption of it in purple2.

Also the IEEE and Stack Overflow surveys from 2022 have Perl ranked between the
20th and 30th most popular programming language so I feel comfortable remove it.

If necessary we can always pull back out of version control and bring it back up
to date.

Testing Done:
Compiled

Reviewed at https://reviews.imfreedom.org/r/1793/