This does a few things.
- Change the place Perl's section 1 man page are installed so that they don't conflict between versions, they get installed at the same place the section 3 man pages are, which seems sensible.
- Only the default Perl, that is, the one defined by DEFAULT_VERSIONS+=perl5=5.xx installs /usr/local/bin/perl.
- The non default Perl do install the usual scripts in /usr/local/bin, but they are installed with a version prefix.