#!/usr/bin/perl

# http://perlmonks.org/?node_id=1185923

use strict;
use warnings;

my @array1 = ("one", "two", "three", "four", "five");
my @array2 = ("banana", "pear", "apple");

my %hash = (
    numbers => \@array1,
    fruit => \@array2
);

# make a reverse lookup hash

my %reverse;
for my $key (keys %hash)
  {
  push @{ $reverse{$_} }, $key for @{ $hash{$key} };
  }

# then do direct lookup ( you may get multiple values, or none )

print "banana -> @{ $reverse{'banana'} // [] }\n";