open my $FHOUT, ">datei";
%zuordn=("m","MPZ","a","APZ","b","BPZ",5,"XXX",7,"ABC","c","DEF");
while (<$FH>){
  @line=split;
  for $i (0 .. 3){
    $line[$i]=$zuordn{$line[$i]};
  }
  $outline=join " ",@line;
  print $FHOUT "$outline\n";
}