After having searched for a while and trying to figure it out, I am at the mercy of Perl Monks. Here is the code that should effectively right rotate $p, bitwise, by 1 spot each time through the loop:

for($a = 0; $a < ($n % $SIZE); $a++)
{
    $carry = 0x1 & $p; #extract least significant bit
    $p >>= 1; #shift $p by one spot to the right
    if($carry == 1) #to rotate in a leading 1
    {
        my $or = 2 ** ($SIZE - 1); #$SIZE is # of bits in $p
        print "OR: $or\n";
        print "pre|: $p. carry: $carry\n";
        $p |= $or; #bitwise or in $or to add the leading 1 to $p
    }
    print "$a-$p\n";
}

[download]
I am using Perl 5.6.1. Here are some sample outputs for a given $p.

#this case works when $SIZE = 32 and $n = 3
p: 204229738. #ok
0-102114869 #ok, carry was 0 before 1st shift
OR: 2147483648 #carry is 1 before 2nd shift
pre|: 51057434. carry: 1 #p after second shift
1-2198541082 #p after | with $or
2-1099270541 #p after third shift

#this case fails when $SIZE = 40 and $n = 1
p: 418262508595. #ok
OR: 549755813888 #ok
pre|: 2147483647. carry: 1 #not ok
0-4294967295 #not ok

It seems that anything of size 5 bytes or greater fails consistently. Any thoughts why and how to combat this?

In reply to Bitwise ops inconsistent by smrtdrmmr

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