my %data;

foreach my $line (@data)
{
     my ($timestamp, $page, $moredata) = split('|', $line);
     my @hits = localtime($timestamp);

     $data{$page} = [0,0,0,0];

     $data{$page}[0]++ if ($hits[7] == $now[7]);
     # ... (etc)
}
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my @now = localtime( time );
my %container; # use this rather than a symbolic ref
foreach my $line ( @data ) {
    my ( $timestamp, $page, $moredata ) = split /|/, $line;
    my @hits = localtime( $timestamp );
    
    $container{$page}[0]++ if $hits[7] == $now[7];
    $container{$page}[1]++ if $hits[4] == $now[4];
    $container{$page}[2]++ if $hits[5] == $now[5];
    $maxCount{$page}++;
}

my @pages = keys %maxCount;

my ( @dAry, @wAry, @mAry );

foreach my $page ( keys %maxCount ) {
    push @dAry, $container{$page}[0];
    push @wAry, $container{$page}[1];    
    push @mAry, $container{$page}[2];
}

my $dAry = join ',', @dAry;
my $wAry = join ',', @wAry;
my $mAry = join ',', @mAry;
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I'm curious, because this part:

   (my $timestamp, my $page, my $moredata) = split('\|',$line);
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   @$page = (0,0,0,0) if ($$page[3] eq '');
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Then there's this third part a few lines later, which could coexist with either of the previous two:

   $maxCount{'$page'}++;
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So, okay, I guess it might work fine without "use strict"; the point is that strings read from input data have nothing to do with the names of variables here. When you use strict, the anon.array held in $page goes out of scope, has no other references to its content, and is reaped.

I would propose an alternate form for the first for loop that would make more sense: creating a new array, and setting the value of a hash element to be a reference to that array, or something of that nature -- but I can't quite make out your intentions in that code... Still, here's a try:

foreach my $line (@data) {
    (my $timestamp, my $page, my $moredata) = split('\|',$line);
    my @hits = localtime($timestamp);
    # Here I create and preset an array with a variable name defined b
+y $page
    my @counters = (0,0,0,0);
    if ($hits[7] == $now[7]) { $counters[0]++; }
    if ($hits[4] == $now[4]) { $counters[1]++; }
    if ($hits[5] == $now[5]) { $counters[2]++; }
    $maxCount{$page} = \@counters;
}

my $dAry = "";  my $wAry = "";  my $mAry = "";
foreach my $page (keys %maxCount) {
    my @counters = @{$maxcount{$page}};
    $dAry .= "$counters[0],";
    $wAry .= "$counters[1],";
    $mAry .= "$counters[2],";
}
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One way to do this is to use another hash.

There are a few notes in the comments.

#!/usr/bin/perl
use strict;
my $datafile = "data.txt";
my @now = localtime(time);

open(FIL,"<$datafile") or die "Can't open data file: $!\n";
my @data = <FIL>;
close(FIL);

my %maxCount;
my %pages;
foreach my $line (@data) {
    # My is a function and will take a list arguement.
    my ($timestamp, $page, $moredata) = split('\|',$line);

    my @hits = localtime($timestamp);
    # Here I create and preset an array with a variable name defined b
+y $page
    ### @$page = (0,0,0,0) if ($$page[3] eq '');

    #Its not quite clear to me when $$page[3] gets set??? Maybe this i
+s something like what you want?
    $pages{$page} = [] unless exists $pages{$page};

    if ($hits[7] == $now[7]) { $pages{$page}[0]++; }
    if ($hits[4] == $now[4]) { $pages{$page}[1]++; }
    if ($hits[5] == $now[5]) { $pages{$page}[2]++; }
    $maxCount{'$page'}++;
}

# Not everyone would endorse this form of list initialisation
my ($dAry, $wAry, $mAry)  = ('','','');

foreach my $page (keys %pages) {
    $dAry .= "$pages{$page}[0],";
    $wAry .= "$pages{$page}[1],";
    $mAry .= "$pages{$page}[2],";
}

#... continued
exit;
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Well, yes!

Untested code:

my %pages;
$pages{"page1"} = [ 1,2,3];
$pages{"page2"} = [ 5,6,7];

print $pages{"page1"}->[1];
print $pages{"page2"}->[2];
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What you are looking for is a hash of arrays, which is a common perl idiom. Check out the perldsc and perllol manual pages.

1. It is better practice to use 'use strict' all the time. We Perl programmers should grab each opportunity to prove to others, that we can code with a style.
2. As for whether you can nest hashes, arrays and lists. The answer is yes, as long as you be careful, and use references properly.

strict is now applied and all is working well. It took a little time but also highlighted a few not so obvious errors. Your responses also gave me some good tips and left me with a couple of questions.

What's the difference between these two lines of code and why use the first when the second will work?

(my $timestamp,my $page,my $userURL,etc) = split('\|',$line);
my ($timestamp,$page,$userURL,etc) = split('\|',$line); # which is muc
+h cleaner.
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my ($var1,$var2,$var3) = ('','','');
my ($var4,$var5,$var6);
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BTW, that looks like you're doing a test on an uninitialized array element (graff)
You're right!
So!! Another good tip on an in-line initilizing technique. (BrowserUk)

my %hits
for (....) {
    ..
    $hits{$page} = [0,0,0,0] unless exists $hits{$page};
    $hits($page}[0]++;
    ..
}
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print $pages{"page1"}->[1];
print $pages{"page1'}[1];
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