Some general thoughts. I don't know much about this general topic, but looking at HTTP::Request::Common, I see that while the discussion therein of the POST method has many text examples in the
    POST $url, Header => Value,...
    POST $url, $form_ref, Header => Value,...
format, the actual function invocation examples all look like
    $request = HTTP::Request::Common::POST( $url, [ %data ] );
or
    $ua->request(POST 'http://somewhere/foo', [foo => bar, bar => foo]);
etc., so this "array" (which might be better thought of as a list of paired items) is always passed as an array reference.

Because it's easy in Perl for a function to look at its arguments at run-time and determine if an argument is a simple scalar or some kind of reference and take alternative action accordingly, functions with complex argument lists are often written so that a particular function  foo() can be called as any of
    foo($string, [ qw(list of stuff) ]);
    foo($string, $another_string, [ %hash ]);
    foo($string, $second_string, $third_string, \@array);
etc., where the expressions  [ qw(list of stuff) ] and  [ %hash ] and  \@array all produce array references.

BTW:   Please don't post text with fields like [some text here] because the  [ ] (square brackets) are markup and just create links to nowhere. (Update: Please see Writeup Formatting Tips and Markup in the Monastery.)