#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dump;

sub collectLeaves ($) {
    my ( $ds, $leaves ) = @_;
    $leaves = defined($leaves) ? $leaves : [];
    if ( ref $ds eq 'ARRAY' ) {
        &collectLeaves( $_, $leaves ) for ( @{$ds} );
    }
    elsif ( ref $ds eq 'HASH' ) {
        &collectLeaves( $ds->{$_}, $leaves ) for ( keys %{$ds} );
    }
    else {
        push @{$leaves}, $ds;
    }
    return @{$leaves};
}

my $hash = {
    key1 => [ 3,4,5,6 ],
    key2 => [ 7,8,9,10 ],
    key3 => [
        d1 => {
            42 => [ 'blue' ],
            58 => [ 7 ],
        }
    ]
};

my @wanted = grep { $_ == 7 } collectLeaves $hash;

dd @wanted;

# (7, 7)