It does mean that 1 && 2 evaluates to true. And, were Perl to have Fortran-style logical comparison operators (.EQV. and .NEQV.; this gives me an idea for an Acme module...), 1 eqv 2 would evaluate to true.

Every language has its little corners which may not be that well thought out; undef& == 0 evaluating to true may be one of them (0⁰ evaluating to 1 is probably another). It is consistent, and arguably reasonable, behavior, although it's just as sensible, and arguably more reasonable, to have undef behave like NaN and not be comparable to anything, even itself (NaN == NaN and NaN != NaN are both false in most languages).