# Sorry about the MANY keyword - I would choose a better name
# for the secondary data, but I have no clue what would make
# sense.
my %keyhash = ( $id => { NAME => $name,
		         REF  => $ref,
                         MANY => []
                       }
              );

##</code><code>##

for ( @array1 ) {
  my ($id,$name,$ref) = split /,/;
  # You may wish to add some error checking to make sure the
  # hash key $id does not already exist
  $keyhash{$id} = { NAME => $name,
		    REF  => $ref,
		    MANY => [],
                  }
}

for ( @array2 ) {
  my ($id,$name,$ref) = split /,/;
  # Warn and do nothing if a record is found for which the
  # $id is not already in %keyhash
  unless ( defined( $keyhash{$id} ) ) {
    warn "No such record $id!\n";
    next;
  }
  push @{$keyhash{$id}{MANY}}, [ $name, $ref ];
}

##</code><code>##

# A little something to get the plurality correct
for ( keys %keyhash ) {
  my $num = @{$keyhash{$_}{MANY}};
  printf "%s appeared %d %s\n",
	$_,
	$num,
	$num > 1 ? "times" : "time";
}