use strict;
use warnings;

package LogKlasse;

my $fh = *STDERR;

sub new { bless {}, shift }
sub writeErr {
    print {$fh} $_[1], "\n";
}

package main;

my $log = new LogKlasse;
$log->writeErr("Fehler Nr.1");

open( FILE, "<notarealfile.txt" ) || die $log->writeErr("Fehler Nr.2");

close FILE;