ManFromNeptune has asked for the wisdom of the Perl Monks concerning the following question:

Here's a problem that has dogged me for years. I want to be able to define a string that contains regex criteria, and then use that within an actual regex expression. For example: 

$criteria = "(abc|123)\$";
$teststring = "Foo walks up and says: abc";

if ( $teststring =~ /$criteria/ ) {
      print "it worked!\n";
}

[download]

Problem is, it doesn't work. A workaround is to not use the parenthesis in the $criteria and instead do: 
$teststring =~ /($criteria)/

[download]
....but that seems like a hack. Is there a better way to do this aside from eval (which has its own problems, particularly if $criteria is being defined through a user-specified value from a web page).

thanks
Nept

Replies are listed 'Best First'.
Re: $scaler inside a RegEx
by mikeraz (Friar) on Aug 05, 2005 at 00:15 UTC

    It doesn't? 

    mikeraz@tire:~$ cat tpl
#!/usr/bin/perl

$criteria = "(abc|123)\$";
$teststring = "Foo walks up and says: abc";

if ( $teststring =~ /$criteria/ ) {
      print "it worked!\n";
      } else {
      print "uh no, it did not\n";
      }
mikeraz@tire:~$ ./tpl
it worked!
mikeraz@tire:~$

    [download]

    is there more code around or between the statements?

    Be Appropriate && Follow Your Curiosity
[reply]
[d/l]
      Better yet: 
      $criteria = "(abc|123)\$";
$teststring = "Foo walks up and says: abc";

if ( $teststring =~ /$criteria/ ) {
   print "Got $1\n";
} else {
   print "uh no, it did not\n";
}

__END__
output
======
Got abc

      [download]
      You might have an easier time at typing your regexp if you used qr// instead of double quotes: 
      $criteria = qr/(abc|123)$/;
...

      [download]
[reply]
[d/l]
[select]
Re: $scaler inside a RegEx
by polypompholyx (Chaplain) on Aug 05, 2005 at 10:47 UTC
[reply]

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