$ perl
use strict;
use warnings;

my %test = (
    foo => 'bar',
    foo1 => 'bar1',
    foo2 => 'bar2',
    foo3 => 'bar3',
);
my @keys = keys %test;
foreach my $temp (@keys) {
    print "Bearbeite '$temp'\n";
    delete $keys[2];
}
__END__
Bearbeite 'foo3'
Bearbeite 'foo'
Use of uninitialized value $temp in concatenation (.) or string at - line 12.
Bearbeite ''
Bearbeite 'foo1'