#!/usr/bin/perl
use strict;
use warnings;

# ----------------------------------------------
# make dummy data
# ----------------------------------------------
my @data;
foreach (1..500) {
    push @data,int(rand(50)+1);
}

# ----------------------------------------------
# analyze data
# ----------------------------------------------

# what are the limits of my data, and define hash 
# (all in one!)
my $min;
my $max;
my %hist;
my $most=0;
foreach my $datum (@data) {
    $min = $datum if ! defined $min || $min > $datum;    
    $max = $datum if ! defined $max || $max < $datum;    
    $hist{$datum}++;
    $most = $hist{$datum} if $most < $hist{$datum};
}

# ----------------------------------------------
# print the histogram
# ----------------------------------------------
print "\n\n";
no warnings 'uninitialized';            # UPDATED
foreach my $m (0 .. $most-1) {
    printf "%05d   ",$most-$m;
    foreach my $i ($min .. $max) {      # UPDATED
        if ($hist{$i} >= ($most-$m)) {
            print "x";
        }
        else {
            print " ";
        }
    }
    print "\n";
}
print "     $min"," "x($max-$min),"$max\n";
[download]

UPDATE

Note that there was no attempt to scale the output. I leave that up to you.