print "Colors: " . (join ",", @{$products->{color}})."\n";
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So easy...and yet I couldn't figure this out on my own.

This simple solution worked wonderfully!

Thanks a ton, vroom

look, $products->{colors} is actually a reference to an array. @{ } does dereferencing of a reference. I suggest you to spend 20 mins on perldoc perlreftut. It is small indeed.

The word is iterating

Remember how you dereferenced product?

 (@{$file->{product}})
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Okay. So I've done a bit of research with ForceArray, but can't seem to make headway with this. When it comes to an item with a single entry like this:

    <product>
        <title>widget3</title>
        <cost>0.50</cost>
        <rating>S</rating>
        <color>white</color>
    </product>
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it returns empty. I have been poking around with my code, but can't seem to get ForceArray to return single item entries. I'm sooo close, yet sooo far...

I don't understand the question.

If you use ForceArray => [qw( product color )],

foreach $products (@{$file->{product}})    {
    print "Widget: " . $products->{title} ." \n";
    print "Rating: " . $products->{rating} . "\n";
    print "  Cost: " . $products->{cost} . "\n";
    print "Colors: " . join(', ', @{$products->{color}})."\n\n";
}
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will work for

<shelf>
    <product>
        <title>widget3</title>
        <cost>0.50</cost>
        <rating>S</rating>
        <color>white</color>
    </product>
</shelf>
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and

<shelf>
    <product>
        <title>widget1</title>
        <cost>0.10</cost>
        <rating>B</rating>
        <color>red</color>
        <color>blue</color>
        <color>green</color>
    </product>

    <product>
        <title>widget2</title>
        <cost>0.25</cost>
        <rating>S</rating>
        <color>pink</color>
        <color>gray</color>
        <color>orange</color>
    </product>
</shelf>
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and everything in between. Without ForceArray, you'd need

sub list {
   if (defined(ref($_[0])) && ref($_[0]) eq 'ARRAY') {
      return @{ $_[0] };
   } else {
      return $_[0];
   }
}

foreach $products (list($file->{product}))    {
    print "Widget: " . $products->{title} ." \n";
    print "Rating: " . $products->{rating} . "\n";
    print "  Cost: " . $products->{cost} . "\n";
    print "Colors: " . join(', ', list($products->{color}))."\n\n";
}
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So what's the problem?

foreach $color (@{products->{color}}) { print $color." " };
print;
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As you’ll see for yourself when you read the tutorials, References are the “magic pixie dust” that lets Perl handle arbitrary data structures easily.   A reference is “a single thing” (therefore, “that lives in one place,” much like a scalar...) that refers to something else.   Vaguely like a C “pointer,” but infinitely more robust...

One of the key notions in Perl is that of contexts.   If you refer to, say, an array-ref “in a scalar context,” you will see “a single thing” that looks like ARRAY(0..) or what-have-you.   Or maybe you get “the number of elements in the array.”   Your mileage may vary.   But anyhow, when you use an array-ref “in an array context,” you get the array of values to which it refers.   And this, basically, is what the notion of dereferencing is all about.

First, you say “Huh?”   Then, you say “Oh, okay, now I get it ... Say, This Is Cool!!”   And so it is.

Nit 1: A reference is not "much like a scalar", it is a type of scalar.

Nit 2: Seeing ARRAY(0..) has nothing to do with context. An array reference is a value; it is not an operator. Context doesn't apply since it's not evaluated. Seeing ARRAY(0..) is the result of stringifying an array reference.