You can be a little more descriptive in the Titles of your nodes. But anyhow try this:

my $a = 'wolf';
$a = $a . ".pl";
[download]

The . is the concatenation operator so the code above does the following:
1. Assigns 'wolf' to $a
2. concatenates what is $a to ".pl" (using the . operator in between).
3. assigns the concatenated string to $a (string being "wolf.pl"

it would not show up (though I don't think the code you posted would work)

Update: Definately more descriptive than "simple question".

-enlil