The following short CGI script should (barring typos) echo back the data that you submit to it. Save it somewhere, make it executable so it runs, write an HTML form that submits to this script, and see what you get.
#! /usr/bin/perl
use strict;
use CGI qw(header param);
print header(type => "text/plain");
foreach my $param (param()) {
print "$param:\n";
foreach my $value (param($param)) {
print " $value:\n";
}
}