# since this is messy and we need to use it a bunch of times, let's load it into a scalar.
my $val = "[a-z0-9?]+=\-%"; # there is no way in heck this is correct; it's a *beginning* though
# get input

if (is_url($string)) {
	# do something with it
}

...

sub is_url {
	my $input = shift;
	$input =~ #(?:http(?:s)|ftp)://$val+\.$val+#i;
}