I'm not convinced that so called "compiled regular expressions" are significantly faster. Here's a benchmark, matching IP addresses. One using the 'variable' approach, and one using compiled regular expressions: 
#!/usr/bin/perl

use strict;
use warnings 'all';
 
use Benchmark;
 
use vars qw /$ip_v $ip_re @data/;

my $quad_v   = q  '(?:25[0-5]|2[0-4]\d|1\d\d|\d\d?)';
my $quad_re  = qr '(?:25[0-5]|2[0-4]\d|1\d\d|\d\d?)';
 
my $sep_v    = q  '\.';
my $sep_re   = qr '\.';
 
   $ip_v     = qq "$quad_v$sep_v$quad_v$sep_v$quad_v$sep_v$quad_v";   
+          
   $ip_re    = qr "$quad_re$sep_re$quad_re$sep_re$quad_re$sep_re$quad_
+re";
 
   @data = map {join "." => map {int rand 1000} 1 .. 4} 1 .. 1_000; 
 
timethese -5 => {
    var  =>  'for (@data) {/$ip_v/}',
    re   =>  'for (@data) {/$ip_re/}',
};
__END__

[download]
Running this results in: 
Benchmark: running re, var for at least 5 CPU seconds...
        re:  5 wallclock secs ( 5.25 usr +  0.00 sys =  5.25 CPU) @ 46.10/s (n=242)
       var:  5 wallclock secs ( 5.16 usr +  0.00 sys =  5.16 CPU) @ 45.93/s (n=237)
Not what I call a significant win for compiled regular expressions. Perhaps you have examples where the gain is large - I've yet to encounter them.

Abigail

In reply to Re: RegEx Perl Code by Abigail-II
in thread RegEx Perl Code by Jaspersan

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