Besides the performance issue you mentioned, I don't even think that your code works.

You need to fix couple of things:

1. you need & not |
2. you need to do an ord()

Test this:

my $c = chr(0xff);
my $sum = 0;
if ($c) {
    (ord($c) & 0x01) && ($sum++); 
    (ord($c) & 0x02) && ($sum++); 
    (ord($c) & 0x04) && ($sum++); 
    (ord($c) & 0x08) && ($sum++); 
    (ord($c) & 0x10) && ($sum++); 
    (ord($c) & 0x20) && ($sum++); 
    (ord($c) & 0x40) && ($sum++); 
    (ord($c) & 0x80) && ($sum++); 
}
print $sum;
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Your code would look like this (there is no need to count the size of the file, I leave it to you to fix the performance)

use strict;
use warnings;

open(FIN,"perl.exe") or die "cant open file\n"; 
my $sum = 0;
my $c;
while (read(FIN, $c, 1)) {
    if ($c) {
        (ord($c) & 0x01) && ($sum++); 
        (ord($c) & 0x02) && ($sum++); 
        (ord($c) & 0x04) && ($sum++); 
        (ord($c) & 0x08) && ($sum++); 
        (ord($c) & 0x10) && ($sum++); 
        (ord($c) & 0x20) && ($sum++); 
        (ord($c) & 0x40) && ($sum++); 
        (ord($c) & 0x80) && ($sum++); 
    }
} 
print "$sum bits are set\n";
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