use strict;
use warnings;

my $temp = 'Plugh';
my $str = <<STR;
To %ad or not to %ad,
that is the question.
Oh %ad on you.
STR

$str =~ s/%ad/$temp/g;
print $str;

##</code><code>##

To Plugh or not to Plugh,
that is the question.
Oh Plugh on you.