Something like this?

my %hash = (
    'foo' => 'bar',
    'Foo' => 'Bar',
    'FOO' => 'BAR',
    );

my $string = "foo Foo foo FOO";

print "old: $string\n";
foreach (keys %hash)
{
    $string =~ s/($_)/$hash{$1}/g;
}

print "new: $string\n";
[download]

old: foo Foo foo FOO
new: bar Bar bar BAR

Jason L. Froebe

Update: I should have read the question more carefully. Follow the second reply (written by Duff).. this one would do better for having a list of tokens that would be replaced with the real values.