[flakes]

A lot of languages have no boolean primitive to begin with. Often in older languages, the values for `true` and `false` are aliases for `0` and `1` respectively. Perl and earlier versions of C, Python, and JavaScript are notable.

Perl is probably the most awkward due to context-sensitive casting. e.g. the string `"0"` in a boolean context evaluates as an integer, and the boolean interpretation for `0` is false.

[int_19h]

JavaScript had Booleans as a primitive type as far back as I can remember. The problem, rather, is that it's altogether too eager to convert everything into everything else.

[erik_seaberg]

Sometimes Perl uses "0E0" as a value that is equal to zero yet not false. Javascript has even more cases where equality isn't transitive.