If you're using one of the latest firmwares, opening an xterm and doing a 'perl -v' should give you info on the installed Perl interpreter. Perl is required by some of the system utilities, so you probably won't see it in App Manager unless it's in Red Pill mode. But you shouldn't need to install the interpreter. it should already be there. Pure Perl modules should work, but you'll need to compile C-based modules for ARM.