use warnings;                   # **
use strict;                     # **

my $data;                       # **
my $c = 0;                      # **
my $outfile = 'tempo.pk';       # **
my $infile = shift;             # **

open(IN,  " < $infile" );
binmode(IN);                    # ** prevents newline translation
my $si=2;   # the number of entries is known
my %matrix;
while($c<$si) {                 # ** removed my
    read(IN, my $bin, 4);
    $data = unpack('N', $bin);  

    my $d = Unshuffle($c);

    print "$c -> $d ($data)\n";  # **
    $matrix{$d} += $data/3;      # **

    $c++;
}
close( IN );
open(OUT, " >$outfile" );
foreach my $d (sort {$a <=> $b} (keys %matrix)) {
    print "$outfile $d ($matrix{$d})\n"; # **
    print (OUT pack('V', $matrix{$d}));
}
close( OUT );

open(IN, " <$outfile" );         # **
while( read(IN, my $bin, 4) ) {  # **
   $data = unpack('V', $bin);    # **
   print "$data:";               # **
}                                # **


sub Unshuffle { # ** interchange the first two positions
   my $val = shift;
   return 1   if ($val == 0);
   return 0   if ($val == 1);
   return $val;
}
# output was
#  0 -> 1 (2140)
#  1 -> 0 (1544028160)
#  tempo.pk 0 (514676053.333333)
#  tempo.pk 1 (713.333333333333)
#  514676053:713: