$ perl -wE'
my $s = "Ö";
my $regex = "ö";
say 1 if $s =~ m/$regex/i'
$ perl -wE'
use utf8; # strings direkt im skript werden automatisch dekodiert
my $s = "Ö";
my $regex = "ö";
say 1 if $s =~ m/$regex/i'
1
$ perl -wE'
use Encode; # manuelles dekodieren von variablen
my $s = decode_utf8 "Ö";
my $regex = decode_utf8 "ö";
say 1 if $s =~ m/$regex/i'
1