/usr/bin/perl isn't a perl binary in this case, but what appears to be a wrapper that calls whichever version of perl is configured. I don't know how that is configured, though the answer here for python can probably be adapted.

If you run VERSIONER_DEBUG=1 perl -v you'll see some of the output from this process.

The actual perl binaries are this small because perl was built with -Duseshrplib which moves most of perl into a shared library. This is common for vendor built perls, since it allows the same shared library to be shared between the perl binary and embedded perls, such as mod_perl2. It can also simplify security updates, since minor fixes only require updating the perl package including the shared library.

I don't know why there are two versions installed