And the reason is that it's supposed to be a "bitstring" not "numeric bit" operation.

see https://perldoc.perl.org/perlop#Bitwise-String-Operators

hence replacing | with |. under use feature "bitwise" will stop doing hard to predict things, even after refactoring this golfing code.

ugh...

That's why the original code very intentionally |'s together two results of the (higher precedence) concatenation operator '.' - which always produces a "string" and not a "number".

voodoo89 tybalt89

guess what, refactoring fails,

      my $copy1b = '0' . $copy1;
      my $copy2b = $copy2 . $_;
      
      $n = ($copy1b | $copy2b);
[download]

copying it literally into the debugger too

  DB<38> say (0 . "$_" | 1 . "1") for qw/0 2 4 6 8/ 
11
11
15
15
11
[download]

The only fix is using |. and use feature 'bitwise';

  DB<39> use feature 'bitwise'; say (0 . "$_" |. 1 . "1") for qw/0 2 4
+ 6 8/ 
11
13
15
17
19
[download]

> voodoo89

Yeah, now go back and sacrifice 89 more chickens to the god of golf ;-P

Cheers Rolf
_{(addicted to the Perl Programming Language :)
see Wikisyntax for the Monastery}