#!/usr/bin/perl -wT
use strict;

my $prefix = 'dog';
my %hash = map {++$;,$_} (qw(ged house ma matic),'');
print "Before:\n";
print "$_ => '$hash{$_}'\n" for keys %hash;

s//$prefix/for values%hash;   # Add the Prefix...

print "\nAfter:\n";
print "$_ => '$hash{$_}'\n" for keys %hash;

__END__

Before:
1 => 'ged'
2 => 'house'
3 => 'ma'
4 => 'matic'
5 => ''

After:
1 => 'dogged'
2 => 'doghouse'
3 => 'dogma'
4 => 'dogmatic'
5 => 'dog'