Also, please note that there is a performance penalty if you have perl evaluate something like 
    /$variable/

[download]
every time. If you don't give perl a hint that $variable never changes, it will recompile the regex every time. To avoid that, use 
    /$variable/o

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to tell "this is a variable, but it never changes, so you need to compile it only once". Here's a benchmark program to show the difference: 
    use Benchmark;

    my $qr_regex  = qr/ab{1,}c{1,}/;
    my $str_regex =   "ab{1,}c{1,}";

    my $string = "asdabdabc";

    timethese(10000000, {
      'string'   => sub { $string =~ /$str_regex/  },
      'string/o' => sub { $string =~ /$str_regex/o },
      'qr'       => sub { $string =~ /$qr_regex/   },
           });

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And here are the results: 
Benchmark: timing 10000000 iterations of qr, string, string/o...
        qr: 11 wallclock secs (10.60 usr +  0.00 sys = 
          10.60 CPU) @ 943396.23/s (n=10000000)
    string: 11 wallclock secs (11.80 usr +  0.00 sys = 
          11.80 CPU) @ 847457.63/s (n=10000000)
  string/o:  7 wallclock secs ( 9.40 usr +  0.02 sys =  
           9.42 CP    U) @ 1061571.13/s (n=10000000)

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-- saintmike

In reply to Re: Storing Regex Patterns in Scalars by saintmike
in thread Storing Regex Patterns in Scalars by iana

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