G'day lulz,

Welcome to the Monastery.

Reading an entire logfile into memory prior to processing would be very much the exception; the norm would be to process the file a line at a time.

The format of each log entry is defined in the Apache configuration file (httpd.conf or whatever you've called it). From my httpd.conf, here's the lines that describe the access_log:

LogFormat "%h %l %u %t \"%r\" %>s %b" common
...
CustomLog "/private/var/log/apache2/access_log" common
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See the documentation in Apache Module mod_log_config for a description of the %X codes and other related information.

With that information to hand, it's fairly easy to construct a regex to parse the log records. Here's a script to do that. The three DATA lines are taken verbatim from my access_log file.

#!/usr/bin/env perl

use strict;
use warnings;

# LogFormat "%h %l %u %t \"%r\" %>s %b" common
my $re = qr{
    ^
    ( \S+ )                     # capture remote host (%h)
    \s+
    ( \S+ )                     # capture remote logname (%l)
    \s+
    ( \S+ )                     # capture remote user (%u)
    \s+
    \[
    ( [^\]]+ )                  # capture request time (%t) without br
+ackets
    \]
    \s+
    "
    ( (?: [^"\\]++ | \\. )*+ )  # capture first line of request (%r)
    "
    \s+
    ( \d+ )                     # capture final status (%>s)
    \s+
    ( \d+ )                     # capture response size in bytes (%b)
    $
}x;

my $format = join '',
    "Host:    %s\n",
    "Logname: %s\n",
    "User:    %s\n",
    "Time:    %s\n",
    "Request: %s\n",
    "Status:  %d\n",
    "Size:    %d\n\n";

printf $format, /$re/ while <DATA>;


__DATA__
127.0.0.1 - - [22/Apr/2015:13:35:04 +1000] "GET /bin/admin.pl HTTP/1.1
+" 401 509
127.0.0.1 - ken [22/Apr/2015:13:35:21 +1000] "GET /bin/admin.pl HTTP/1
+.1" 500 656
127.0.0.1 - - [24/Apr/2015:04:51:49 +1000] "GET / HTTP/1.1" 200 45
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Output:

Host:    127.0.0.1
Logname: -
User:    -
Time:    22/Apr/2015:13:35:04 +1000
Request: GET /bin/admin.pl HTTP/1.1
Status:  401
Size:    509

Host:    127.0.0.1
Logname: -
User:    ken
Time:    22/Apr/2015:13:35:21 +1000
Request: GET /bin/admin.pl HTTP/1.1
Status:  500
Size:    656

Host:    127.0.0.1
Logname: -
User:    -
Time:    24/Apr/2015:04:51:49 +1000
Request: GET / HTTP/1.1
Status:  200
Size:    45
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Be aware that your configuration may use other logfiles with different LogFormat directives; however, you should be able to contruct a suitable regex using the script above as a template. And, of course, you'll probably want to do something more useful than just printing the data.