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    <p>There are two ways you can do this: </p> <ol> <li>by prototype</li> <li>by reference</li> </ol> <p>But before I discuss these--if what you show in your question is about the extent of what you want to do--let me suggest <a href="http://search.cpan.org/perldoc?List::MoreUtils#pairwise" rel="nofollow noreferrer"><code>List::MoreUtils::pairwise</code></a></p> <p>So, where you would write this:</p> <pre><code>my @sum = two_array_sum( @a, @b ) </code></pre> <p>You'd simply write this: </p> <pre><code>my @sum = pairwise { $a + $b } @a, @b; </code></pre> <h3>By prototype</h3> <p>This works like <code>push</code>. (And just like <code>push</code> it demands to have a <code>@</code> sigil on <em>something</em>)</p> <pre><code>sub two_array_sub (\@\@) { my ( $aref, $bref ) = @_; ... } </code></pre> <p>That way when you do this</p> <pre><code>two_array_sub( @a, @b ); </code></pre> <p>it works. Whereas normally it would just show up in your sub as one long list. They aren't for everybody as you'll see in my discussion below.</p> <h3>By reference</h3> <p>That's the way that everybody is showing you. </p> <pre><code>some_sub( \@a, \@b ); </code></pre> <h3>About prototypes</h3> <p>They're finicky. This won't work if you have refs:</p> <pre><code>two_array_sub( $arr_ref, $brr_ref ); </code></pre> <p>You have to pass them like this:</p> <pre><code>two_array_sub( @$arr_ref, @$brr_ref ); </code></pre> <p>However, because making "array expressions" gets <em>really</em> ugly quickly with arrays nested deep, I often avoid Perl's fussiness as you can overload the type of reference Perl will take by putting it in a "character class" construct. <code>\[$@]</code> means that the reference can either be a scalar or array.</p> <pre><code>sub new_two_array_sub (\[$@]\[$@]) { my $ref = shift; my $arr = ref( $ref ) eq 'ARRAY' ? $ref : $$ref; # ref -&gt; 'REF'; $ref = shift; my $brr = ref( $ref ) eq 'ARRAY' ? $ref : $$ref; ... } </code></pre> <p>So all these work: </p> <pre><code>new_two_array_sub( @a, $self-&gt;{a_level}{an_array} ); new_two_array_sub( $arr, @b ); new_two_array_sub( @a, @b ); new_two_array_sub( $arr, $self-&gt;{a_level}{an_array} ); </code></pre> <p>However, Perl is still fussy about this... for some reason:</p> <pre><code>new_two_array_sub( \@a, $b ); OR new_two_array_sub( $a, [ 1..3 ] ); </code></pre> <p>Or any other "constructor" that still could be seen as a reference to an array. Fortunately, you can shut Perl up about that with the old <em>Perl 4</em> <strong><code>&amp;</code></strong></p> <pre><code>&amp;new_two_array_sub( \@a, [ 1..3 ] ); </code></pre> <p>Then the mux-ing code in the sub takes care of handling two array references.</p>
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    1. CO+1 for a much better answer than my quote of the manpage.
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    2. CO+1 for thorough explanation of refs vs prototypes
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