It doesn't pertain to your question but the code:

$string =~ /^[smtwhfa]*$/

The * is zero or more, not one or more. For one or more use the + sign. (So it would be /^[smtwhfa]+$/) Unless instead of saying

"A user supplied string may contain 1 or more of the characters smtwhfa in any order."
you really meant zero or more. Just a frequent mistake some people make that I thought I would point out.

In reply to Re: Regex (lookahead) Confusion by MCS
in thread Regex (lookahead) Confusion by ChrisR

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