$ perl -v | grep version
This is perl 5, version 16, subversion 0 (v5.16.0) built for x86_64-linux
$ locale  | grep LC_CTYPE
LC_CTYPE="en_GB.UTF-8"
$ perl -w -E "use locale; use POSIX qw(locale_h); setlocale(LC_CTYPE,'de_DE.utf-8'); say 'betätigt' ~~ /bet\b/"
1
$ perl -w -E "use POSIX qw(locale_h); setlocale(LC_CTYPE,'de_DE.utf-8'); say 'betätigt' ~~ /bet\b/"

$ perl -w -E "say 'betätigt' ~~ /bet\b/"

$