#!/usr/bin/perl -T
use strict;
use lib '.';
use CGI;
my $cgi = new CGI;
my $plugin = $cgi->param('p');
if($plugin =~ /^([A-Za-z0-9_]+)$/) {
    $plugin = $1;
}
else {
    die "Bad plugin name";
}

require Plugins::$plugin;
# ...

##</code><code>##

my $req = "Plugins::$plugin";
require $req;