Your logic for finding out whether the domain is in the hash is wrong. You should use something like

if (exists $hash{$key}) {
  print "\n";
} else {
  print "\nThe domain you entered is not on the list above ...";
}
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You loop through the keys of your hash, so you take the first key (attention: they are usually not in the same order as you put them in the hash) and compares it to your $selection. Most likely it won't be the same, so your else-part is executed, where you have built in an exit, too, so it prints your failure statement and stops. Even if your $selection is one of your keys, unless it is the first key in the hash, your program won't find it. PS: In general it is not a good idea to name a hash %hash. That it is a hash is shown by the sigil %. Better give it a name that describes what's inside the hash, here an idea would be to call that variable like %domain. Something similiar could be said about $key, but here you could avoid it completely, e.g. to print the list of domains, you could just write print "  $_\n" foreach keys %hash