$file = 'ptc.opt';    
open(INFO, $file);    
@lines = <INFO>;    

my $groupname;

for (my $i=0;$i<@lines;$i++){
  my @reihe = split(/ /, $lines[$i]);    
  my @groupmember;
  if($reihe[0] eq "GROUP"){
       $groupname = $reihe[1];
         for (my $x=0;$x<@reihe;$x++){
              if($x>1){
               push(@groupmember,$reihe[$x]);
               }
       }
  }        
  $groups{$groupname} = [@groupmember];
    
}

foreach $gruppe (keys(%groups)) {
  print "\n".$gruppe.":\n ";
     for(my $g=0;$g<@{$groups{$gruppe}};$g++){
            print @{$groups{$gruppe}}[$g]." ";
     }
}
close(INFO);