#!/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;	

  $elements{$id}=\@words;

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

while( my ($k, $v) = each %elements )
{
  print "key: $k, value: ".join(', ',@$v).".\n";
}