matching german umlaut with regexp correctly twice

i have a small script, which match via regexp if a string contains german umlauts like äöüß. In the first regexp match everything is working fine, but if i check the same string again it does not longer match correctly. The file itself is encoded as utf8 and i am also including the utf8 module.

this is the script:

#!/usr/bin/perl
use strict;
use warnings FATAL => 'all';
use utf8;
use Log4Perl::logger_helper qw( init_logger get_logger_and_trace );

my $strings = ["ä", "ae","ö", "oe", "ü", "ue", "ß", "ss"];

my $logger = init_logger(
    log_file_path => $0 . '.log'
);    # init_logger variables are all optional

foreach my $string (@$strings) {
    for(1..5) {
        if ( $string =~ /[\x{00C4}\x{00E4}\x{00D6}\x{00F6}\x{00DC}\x{00FC}\x{00DF}]/gi ) {
            $logger->info("umlauts match $string");
        }
        else {
            $logger->info("no umlauts $string");
        }
    }
 }

and this is the output:

umlauts match ä
no umlauts ä
umlauts match ä
no umlauts ä
umlauts match ä
no umlauts ae
no umlauts ae
no umlauts ae
no umlauts ae
no umlauts ae
umlauts match ö
no umlauts ö
umlauts match ö
no umlauts ö
umlauts match ö
no umlauts oe
no umlauts oe
no umlauts oe
no umlauts oe
no umlauts oe
umlauts match ü
no umlauts ü
umlauts match ü
no umlauts ü
umlauts match ü
no umlauts ue
no umlauts ue
no umlauts ue
no umlauts ue
no umlauts ue
umlauts match ß
no umlauts ß
umlauts match ß
no umlauts ß
umlauts match ß
no umlauts ss
no umlauts ss
no umlauts ss
no umlauts ss
no umlauts ss

Process finished with exit code 0

I tested it on different OS with different version of strawberry perl, also latest version (strawberry-perl-5.30.0.1-64bit-portable) is shown this error for me.

Any idea why it is matching alterating correctly? If i do the same with multiple index operations it is working.

Thanks in advance.

The problem is the global flag. Remove it.