[Perl 5.14, regex]: Problems with /g, \G and pos()

[Darkwing]

Hi community, this is my very first question here. I have some problems with /g, \G and pos() and i do not understand what's going on (possibly a bug in my version of perl?). Hope someone knows about the following behaviour of perl:

# File: defect1.pl
use strict;
use warnings;

my $str = "  xyz";

$str =~ /^(\s*)/g or die;
print("match1: pos=", pos($str), "\n");

$str =~ /\G(\s*)/g or die;
print("match2: pos=", pos($str), "\n");

$str =~ /\G(\s*)/g or die;
print("match3: pos=", pos($str), "\n");

Output:

match1: pos=2
match2: pos=2
Died at defect1.pl line 13.

Why does the third match fail? I'd expect that after the first regex i could repeat $str=~/\G(\s*)/g again and again, it should always succeed (and never change pos()) since \s* also matches zero occurrences of spaces.

Even worse is this:

use strict;
use warnings;

my $str = "  xyz";
$str =~ /^(\s*)/g;
my ($x) = ($str =~ /\G(x)/g) or die;
defined(pos($str)) or warn("pos() is undefined!\n");
print("this should be x:$x\n");

Output:

pos() is undefined!
this should be x:x

Even though the regex succeeded and $x has the correct value, pos($str) is undefined. Same result from this variant:

use strict;
use warnings;

my $str = "  xyz";
$str =~ /^(\s*)/g;
my $x = ($str =~ /\G(x)/g)[0] or die;
defined(pos($str)) or warn("pos() is undefined!\n");
print("this should be x:$x\n");

Again:

pos() is undefined!
this should be x:x

In contrast, the following works fine:

use strict;
use warnings;

my $str = "  xyz";
$str =~ /^(\s*)/g;
$str =~ /\G(x)/g or die;
my $x = $1;
defined(pos($str)) or warn("pos() is undefined!\n");
print("this should be x:$x\n");

Output:

this should be x:x

Obviously, perl clobbers the position associated with $str as soon as i treat the regex's result as an array - but why? I'm running perl 5.14 on Suse Linux 12.1. perl -v says:

This is perl 5, version 14, subversion 2 (v5.14.2) built for x86_64-li
+nux-thread-multi