It sounds like you want to organize your data as a Hash-of-Arrays structure, which can support multiple values for each key. To retrieve a key corresponding to a value, you could loop through the keys of the hash, then loop through the array elements for each key:

use strict;
use warnings;
use Data::Dumper;

# %data is an example Hash-of-Arrays structure
# where the hash has 3 keys (a,b,c) and each
# key has 3 values:
my %data = (
    a => [1..3],
    b => [4..6],
    c => [7..9],
);
#print Dumper(\%data);

print get_key(3), "\n";
print get_key(8), "\n";
print get_key(0), "\n";

sub get_key {
    my $value = shift;
    for my $key (keys %data) {
        for my $val (@{ $data{$key} }) {
            if ($val eq $value) {
                return $key;
            }
        }
    }
    return 'key not found';
}

__END__

a
c
key not found
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