$ perl -w -e '$a=">äüöÄÜÖ<"; $a =~ s/ä//ig; print $a'
>üöÄÜÖ<
$ perl -MEncode -w -e '$a= decode("Latin-1",">äüöÄÜÖ<"); $a =~ s/ä//ig; print $a'
>üöÜÖ<