If you want to find a substring inside a string, index might be a better choice than a regex (because you don't have to compile the regex, it's probably clearer to other people, and there's less unexpected side effects like metachars):

$string = "This is a non-SENSE sentence";
$substring = "non-sense";
print "Match!" if index(lc $string, lc $substring) >= 0;
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