It's even easier than that! CGI's Vars returns the very hash you're looking for.

#!/usr/bin/perl -wT
use strict;
use CGI qw( header Vars );

my %FORM = Vars();   ### Bingo!

print header( 'text/plain' );
$\ = "\r\n";
use Data::Dumper;
print Dumper(\%FORM);
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