use strict;
use warnings;

while (<DATA>) {
    chomp;
    my ($pat, $repl) = (split '/') [1, 2];
    my $s = "foo";
    $s =~ s/$pat/qq{"$repl"}/ee;
    say $s;
}

__DATA__
s/foo/bar/
s/(fo)o/bar$1/

##</code><code>##

bar
barfo