source: vendor/perl/5.8.8/perlsh

#!/usr/bin/perl

# Poor man's perl shell.

# Simply type two carriage returns every time you want to evaluate.
# Note that it must be a complete perl statement--don't type double
#  carriage return in the middle of a loop.

$/ = "\n\n";    # set paragraph mode
$SHlinesep = "\n";
while (defined($SHcmd = <>)) {
    $/ = $SHlinesep;
    eval $SHcmd; print $@ || "\n";
    $SHlinesep = $/; $/ = '';
}