You could go faster by completing your rangeHash straightaway without going through dataHash first.

Assuming your ranges can't overlap, all you have to do is compute the range from the value and use it as a key. For example: (the getRange sub is far from being perfect, I went for a simple solution since you probably already have code to check which range you are in) : 

use Data::Dumper;

sub getRange
{
  my $value = shift;
  warn "Unexpected value $value," and return if $value < 1;
  return '1-19' if $value < 20;
  return '20-29' if $value < 30;
  return '30-39' if $value < 40;
  return '40-59' if $value < 60;
  warn "Out of range value $value," and return;
}

my %hits;

while (<DATA>)
{
  my $range = getRange($_);
  $hits{$range}++ if defined $range;
}

print Dumper \%hits;

__DATA__
12
14
15
20
21
50
42

[download]
The result is : 
$VAR1 = {
          '1-19' => 3,
          '40-59' => 2,
          '20-29' => 2
        };

[download]

In reply to Re: Perl hit counter for multiple ranges, optimization or options in other languages? by Eily
in thread Perl hit counter for multiple ranges, optimization or options in other languages? by SaktiMonk

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