No. You would simple do the following:

$regex = "ISOLATION";
if ($dataline =~ m/$regex/";
   print "Found a match!\n";
} else {
   print "No match!\n";
}
[download]

Update: Watch my typos there. 2nd line should read if ($dateline =~ m/$regex/) {

$PM = "Perl Monk's";
$MCF = "Most Clueless Friar Abbot";
$nysus = $PM . $MCF;