CGI.pm already does this in a fashion:

<input name='form_item' value='one'>
<input name='form_item' value='two'>
<input name='form_item' value='three'>
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And the resulting Perl:

my $q = new CGI;
print join(",", $q->param('form_item'));  # one,two,three
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In cases where more than one form element uses the same name, CGI.pm will return them as an array, if you call the param method in a list context. Is this what you meant?