#!/usr/bin/perl -w
package control;

use strict;

sub param {
	my $daten = shift();
	$$daten =~ s/a/b/gi;
}
package main;
use strict;
my $daten = "a";
print "daten: $daten\n";
print "-----\n";
control::param(\$daten);
print "daten: $daten\n";