Use a hash to store the data. Hashes are ideal if you have name - value pairs:

my %fields = (
   name => "Richard",
   age  => "12",
   location => "mars",
   forum_user => "xxxxx",
   forum_pass => "yyyyy",
);
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you can pass that on to submit_form easily:

    $mech->submit_form(
        form_name => $search_form,
        fields      => \%fields,  # pass reference to %fields
    );
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See also perldata and perlref