Your regex is really horribly inefficient. Think about what it has to do to match that pattern. A much simpler way to do the same thing is: 

#!/usr/local/bin/perl

use warnings;
use strict;
use English;
use Data::Dumper;
use Time::HiRes 'time';

my $logfile;

my $count = 0;                  # Initialize counter
my $start = time();             # Start the timer

my $fullrec;

while( <DATA>) {
    if (/^\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d:\d\d\d/) {
        $count++;   
        #if ($fullrec) {
        #   process($fullrec);
        #}
        $fullrec = $_;
    } else {
        $fullrec .= $_;
    }
}

#if (defined($fullrec)) {
#   process($fullrec);
#}

my $end = time();               # Stop the timer
my $elapsed = $end - $start;    # How long did that take?
my $average = $elapsed/$count;  # Average processing time

printf "Parsed $count log file entries in %.4f seconds, averaging %.4f
+\n", $elapsed, $average;

exit;


__DATA__
<SNIPPED DATA>

[download]

Ie you know that when a line starts with a data that it begins a record, this also implys it denotes the end of the previous record (if such a record exists). Thus you simply need to check each line to see if it begins the record, and then do something with the previous one that you have constructed. This also means that the pattern is anchored and only needs to compare Lr (the length of pattern) chars per line instead of the the Lf (the length of the file) times Lr that your code would do (with the look ahead assertion).

So your pattern does something like 55000000*23 character lookups, even worse most of those will be char class lookups so they are inefficient to start with. If you use the line by line approach you are dealing with 366000*23 lookups. Thats a LOT less. (Actually these are upper bounds, but i think the point is made)

Update:Fixed as per ikegami's reply.

---
$world=~s/war/peace/g

In reply to Re: Pimp My RegEx by demerphq
in thread Pimp My RegEx by heathen

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