# Modul1.pm
package Porjekt::Modul1;

use strict;

sub new
{
    my($package) = @_;
    my $this = bless({Var1 => 1, Var2 => 2}, $package);
    return $this;
}

1;

# Main.pl
#!/usr/bin/perl -w

use strict;

use Projekt::Modul1;

my $mod1 = Projekt::Modul1->new;

sub TuWas
{
    my($modul) = @_;
}

TuWas($mod1);

TuWas(\$mod1);

#!/usr/bin/perl

my $string = "Hallo";
TuWas($string);
print $string,"\n";

sub TuWas{
    $_[0] = "Perl-Community.de";
}

my $string = "Hallo";
TuWas($string);
print $string,"\n";

sub TuWas{
    my ($string2) = @_;
    $string2 = "Perl-Community.de";
}