my $str = "  xyz"
print "$str\n";

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

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

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