# always use strictures (the following two lines)
use strict; 
use warnings;

my @array = qw(key1 key2 key3 key4);
my %hash = (key2 => undef, key4 => 'The goods', key5 => 'More goods');

doLoop ();

sub doLoop {
    for my $key (@array) {
        next if ! exists $hash{$key}; # Skip if the key is not used in the hash
        next if ! defined $hash{$key}; # Skip if the key exists, but is undefined
        next if $hash{$key} ne 'No goods';
        print "The value for '$key' is '$hash{$key}'\n";
        return;
    }
    
    print "Failed to find matching key\n"
}

##</code><code>##

Failed to find matching key

##</code><code>##

use strict; 
use warnings;

my @array = qw(key1 key2 key3 key4);
my %hash = (key2 => undef, key4 => 'The goods', key5 => 'More goods');
my $match = 0;

for my $key (@array) {
    next if ! exists $hash{$key}; # Skip if the key is not used in the hash
    next if ! defined $hash{$key}; # Skip if the key exists, but is undefined
    next if $hash{$key} ne 'No goods';
    
    print "The value for '$key' is '$hash{$key}'\n";
    $match = 1;
    last;
}

print "Failed to find matching key\n" if ! $match;