I found this post on-line and I am not clear exactly what is going on.

“…you will get a string of bytes with values zero and one, rather then the characters '0' and '1'. To make this printable just 'or' in a string of zeroes of the right length.”

$dd |= '0' x length $dd

I know what the result of this statement is but I am not sure exactly what (how) it is doing (it). I am comparing 2 strings (^) and when I do

$cmp |= '0' x length($cmp); # See rest of code below.

numbers magically appear and I can then see (print) what is in $cmp. So, what exactly does ‘or’ in a string of zeroes mean? Zeroes appear but so do other digits (“A” ^ “C” → 2). What does |= do? (or |= ‘0’) Is there some substitution occurring?

My code: 
$Str1 = "AAAACCCCGGGGTTTT";
$Str2 = "ACGTACGTACGTACGT";

$cmp = $Str1^$Str2;
$cmp |= '0' x length($cmp);

print "$Str1\n";
print "$Str2\n";
print "$cmp\n";

[download]

**OUTPUT**

AAAACCCCGGGGTTTT

ACGTACGTACGTACGT

0265204764035730

grazie,

romano

In reply to bitwise string operator by Anonymous Monk

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