#!/usr/bin/perl
use strict;
use warnings;

my %elements = ();
my $input = $ARGV[0];

my $cnt=0;
open (my $fh, '<', $input) or die("ERROR open $input ($!)\n");
while(my $line=<$fh>)
{
  chomp($line);
  my ($id,@words) = split /\s+/, $line;

  #füge dem hasheintrag "$elements{$id}",
  # welches ein Array ist (siehe Autovivikation),
  # einen weiteren Eintrag hinzu,
  # der das Array "@words" ist.
  push(@{$elements{$id}},\@words);

  $cnt++;
  if ($cnt % 1000000 == 0) {print "read another 1000000 lines!\n";}
}
close($fh);

while( my ($k, $v) = each %elements )
{
  print "key: $k\n";
  for my $i ( 0 .. $#{$v} ) {
    print "  cols $i: ". join( ', ', @{ $v->[$i] } ) ."\n";
  }
}

id1 test1a test1b test1c
id1 test1d test1e test1f
id1 test1g test1h test1i
id2 test2a test2b test2c
id2 test2d test2e test2f
id2 test2g test2h test2i
id3 test3a test3b test3c
id3 test3d test3e test3f
id3 test3g test3h test3i
id4 test4a test4b test4c
id4 test4d test4e test4f
id4 test4g test4h test4i

key: id1
  cols 0: test1a, test1b, test1c
  cols 1: test1d, test1e, test1f
  cols 2: test1g, test1h, test1i
key: id4
  cols 0: test4a, test4b, test4c
  cols 1: test4d, test4e, test4f
  cols 2: test4g, test4h, test4i
key: id2
  cols 0: test2a, test2b, test2c
  cols 1: test2d, test2e, test2f
  cols 2: test2g, test2h, test2i
key: id3
  cols 0: test3a, test3b, test3c
  cols 1: test3d, test3e, test3f
  cols 2: test3g, test3h, test3i

%elements=(
  'id1' => [
             [ 'test1a', 'test1b', 'test1c' ],
             [ 'test1d', 'test1e', 'test1f' ],
             [ 'test1g', 'test1h', 'test1i' ],
           ],
  'id2' => [
             [ 'test2a', 'test2b', 'test2c' ],
             [ 'test2d', 'test2e', 'test2f' ],
             [ 'test2g', 'test2h', 'test2i' ],
           ],
  'id3' => [
             [ 'test3a', 'test3b', 'test3c' ],
             [ 'test3d', 'test3e', 'test3f' ],
             [ 'test3g', 'test3h', 'test3i' ],
           ],
  'id4' => [
             [ 'test4a', 'test4b', 'test4c' ],
             [ 'test4d', 'test4e', 'test4f' ],
             [ 'test4g', 'test4h', 'test4i' ],
           ],
);