#!/usr/bin/perl
use strict;
use warnings;

# Anfangswert setzen
my $fct = foo->new('bar');

# Ausgabe
print $fct->is_equal('bar'),"\n";

# Wert ändern
$fct->set('foobar');

# Ausgabe
print $fct->is_equal('bar'),"\n";


1;

# Funktion
{ package foo;


  sub new {
    my $class = shift;
    my $foo   = shift;
  
    bless \$foo, $class;
  }

  sub is_equal {
    my $class = shift;
    my $bar   = shift;
  
    return 'kein Vergleich möglich' if !$$class;
  
    $bar eq $$class ? 'ja':'nein';
}

  sub set {
    my $class = shift;
    $$class   = shift;
  }

 1;
}