You want an array and you want it pre-seeeded for the 24 values you're looking for. 
my @byhour = (0) x 24;
foreach my $hour (@hours)
{
    my ($knownhour) = $hour =~ /\s(\d\d)/;

    $byhour[$knownhour]++;
}

print "$_ had $byhour[$_]\n" for 0 .. $#byhour;

[download]

Update: Fixed typo caused by not actually trying the code under strict.

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In reply to Re: extracting by date into hour for counting by dragonchild
in thread extracting by date into hour for counting by Anonymous Monk

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