Problem with foreach loop

[HACKER Nora]

Hello list,

Could someone please explain why this test script:

my @arr1 = qw(one two three);
my @arr2 = qw(1 2 3);

foreach my $arr1 ( @arr1 ) {
        print "Arr1: $arr1\n";
        foreach my $arr2 ( @arr2 ) {
                print "Arr2: $arr2\n";
                if ( $arr2 eq '2' ) {
                        shift @arr1;
                }
        }
}

produces that result:

oracle:/opt/data/magna/wartung/work/nora> ./test.pl
Arr1: one
Arr2: 1
Arr2: 2
Arr2: 3
Arr1: three
Arr2: 1
Arr2: 2
Arr2: 3

whereas I had expected the output to be like this:

oracle:/opt/data/magna/wartung/work/nora> ./test.pl
Arr1: one
Arr2: 1
Arr2: 2
Arr2: 3
Arr1: two       # why not?
Arr2: 1         # why not?
Arr2: 2         # why not?
Arr1: three
Arr2: 1
Arr2: 2
Arr2: 3

Thanks in advance!

Regards, 
Nora