Lol, you've got to love a refresher in middle-school math. ;) Thanks.

Taking that into consideration, and adding a built-in string validity check, here's how the working code now looks: 

use strict;
use warnings;
use Carp;

while ( <DATA> ) {
    chomp;
    print "$_\t=>\t", bin_to_dec($_), "\n";
}

sub bin_to_dec {
    our $num;    # $num must be a global to work.
    local $num;  # Play nice if $num is already in global use.
    $_[0] =~ m/ 
                (?=^[10]+$)       # Check for a valid string.
                (?{ $num = 0; })
                (?:
                  ([10])
                  (?{ $num = 2 * $num + $^N; })
                )+
             /x
        or croak "Error: $_[0] is not a pure bit string.\n";
    return $num;
}

__DATA__
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111

[download]

Thanks again...


Dave

In reply to Re^2: Inexplicable uninitialized value when using (?{...}) regexp construct. by davido
in thread Inexplicable uninitialized value when using (?{...}) regexp construct. by davido

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