I ran your code, and it behaves as I would expect. If I type in "barbaz$" or "oob" and hit the $go_button, I get a match, and if I type "foot" or "xyz", I don't get a match. Isn't this exactly what you want?

I am guessing you think the input text has to be wrapped in a qr// for it to work, but that's not the case. You only need to feed a regular-expression string to m//, not a regular-expression object (which you construct with qr//), In fact, since qr// is really just a chunk of perl code, you would need to eval it to get it to work. Replacing the last line of your command sub for $go_button with the following would force users to enter their regular expression using qr//: 
$string =~ eval $exp ? print STDOUT "match!\n" : print STDOUT "No matc
+h!\n";

[download]
It is only by chance that (?-xism:foo) matches "foobarbaz" - it has nothing to do with the fact that this is the string representation of the regular expression qr/foo/. The "(?-xism:" signals the start of a non-capturing grouping with the x, i, s and m modifiers turned off. This little construct is buried within perlre. I can't say I ever realized that the stringification of a regular expression is itself another related, similar regular expression.

Update: Boy do I feel like a fool! Whenever Perl printed (?-xism:the regex), I always read it as "Regular expression-ism: 'the regex'". As in "The United States' policy was one of protectionism". I never realized Perl was being helpful and showing me the modifiers it was (or wasn't) using.

In reply to Re: passing qr//'d regexp via Perl/Tk Entry widget by crashtest
in thread passing qr//'d regexp via Perl/Tk Entry widget by young_stu

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