Don't read the file byte by byte, but read it in larger chunks and have an inner loop counting the characters:

open my $file, '<', shift;
binmode($file);

my %seen = ();

$/ = \( 1024 * 1024 ); # Set default buffer size
while ( <$file> ) {
    for my $buf (split //, $_) {
      if ( !$seen{$buf} ) {
          $seen{$buf} = 1;
      }
      else {
          $seen{$buf}++;
      }
    }
}
print "$_ - $seen{$_}\n" for ( keys %seen );

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In reply to Re: Count byte/character occurrence (quickly) by Corion
in thread Count byte/character occurrence (quickly) by james28909

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