S'funny. It works for me?
$s = 'abc.def';
$s =~ s[(?<=[.])[^.]*$][xyz];
print $s;;
abc.xyz
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.