Okay, in the (probably forlorn) hope of beating this subject to death,
let me offer a possible (post-A3/E3) position on NaN.
NaN is dead.
Except perhaps under a C<use IEEE> pragma of some kind, in which case it
would be a proper IEEE NaN.
C<undef> with numerify to zero (it always has; and we always intended
that it still would).
Unary C<+> (and other numeric contexts) will produce C<undef> when
attempting to convert non-numeric strings.
To check for numericity of input, you'll write:
$number = +<$fh>
until defined $number;
If you ignore the definedness, the C<undef> will just promote to zero
in numeric contexts. So you can add up your column-50 numeric fields with:
$sum += +unpack("@49 A3", $_)
while <$fh>;
and have it ignore non-numeric fields.
Or you can add the fields with:
$sum += +unpack("@49 A3", $_) // die "Bad data: $_"
while <$fh>;
and handle errors with extreme prejudice.
Have I missed anything?
Damian
