Telling Perl to REPL is absolutely insane:
perl -e 'while(<>) { print eval, "\n\n" }'
perl -e 'while(<>) { print eval, "\n\n" }'
Puts you at the step debugger command line, effectively a REPL.
Or use reply: https://metacpan.org/dist/Reply/view/bin/reply
Or use re.pl, included with Devel::REPL: https://metacpan.org/pod/Devel::REPL