#!/usr/bin/perl
use strict;
use warnings;

my %edits = (foo => 'bar', bar => 'foo');
my $value = 'This string is all barfoo, but a little Perl should swap the foos and bars';
my $match = '(' . join ('|', keys %edits) . ')';

$value =~ s/$match/$edits{$1}/g;

print $value;

##</code><code>##

This string is all foobar, but a little Perl should swap the bars and foos