Using formatted numbers has hash keys is not a good idea. The data is not in $hash{00} but in $hash{0}, as 00 is interpreted as a number and not as a string.

When in doubdt about your data try either the perl debugger (run perl -d) or Data::Dumper (or Data::Denter if you have it installed):

#!/bin/perl -w
use strict;
use Data::Dumper;

my @foo = (0,1);
my %hash;

$hash{00} = "data";
$hash{"00"} = "the real one";
$hash{10} = "moredata";

print Dumper( %hash);

print '$hash{0} is ', $hash{0} , "\n";
print '$hash{00} is ', $hash{00} , "\n";
print '$hash{$foo[0] . "0"} is ', $hash{$foo[0] . "0"}, "\n";
print '$hash{$foo[1] . "0"} is ', $hash{$foo[1] . "0"}, "\n";
print '$hash{10} is ', $hash{10} , "\n";
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