It has been on my todo to try the REPL for a long time, but since Perl is the most powerful command line tool in bash, I've never seen a reason to use an interactive tool.
alias p=perl
p -e '...'
p -ne '....'
# etc.
Edit: With powerful I didn't mean "rm -rf", etc. :-)
also you can do this: $ perl -e 'print "Hello World!\n";'