vec($image, $max_x * $x + $y, 8) = 3;

Vectors created with vec() can also be manipulated with the logical operators |, &, and ^, which will assume a bit vector operation is desired when both operands are strings.

To transform a bit vector into a string or array of 0's and 1's, use these:

    $bits = unpack("b*", $vector);
    @bits = split(//, unpack("b*", $vector));

If you know the exact length in bits, it can be used in place of the *.