Learn Perl and rewrite it. Seriously, there's no simple converter. Things
that are awkward to do in the shell are easy to do in Perl, and this very
awkwardness is what would make a shell->perl converter nigh-on
impossible to write. By rewriting it, you'll think about what you're really
trying to do, and hopefully will escape the shell's pipeline datastream
paradigm, which while convenient for some matters, causes many
inefficiencies.