My first suggestion would be to see if there is anything on CPAN that could handle the log entries in a way that would be of use to you. A quick search suggested things like Apache::Logmonster and Apache::ParseLog (among others), and you could look at the source of other modules to see how they may have done it.

A while back, I looked at this kind of thing for my own curiousity. Looking at the code I was playing with, this might be of some usefulness to you:

# usual strict and warnings and such

use Date::Parse;        # to parse the entry date
use Text::ParseWords;   # to handled quoted entries

# $logfile defined in skipped code

open DF, $logfile or die $!;
while (<DF>) {
    chomp;
    # the following conversion is so the date can be
    #   captured intact
    s/(\[|\])/"/g;
    my @part = Text::ParseWords::quotewords( '\s+', 0, $_ );
    $part[3] = str2time( $part[3] );

    # deal with whatever part 
    #   of the log entry here you need

}
close DF;
[download]

Hope that helps.