False values versus Existence: It is, therefore...
Just because something is false doesn't mean to say it doesn't exist. A wig is false hair, but a wig exists. Your variable is still there. Perl does have a function to test if something exists. Existence, in Perl terms, means defined. So:
print "Car is defined !\n" if defined $car;
will evaluate to true, as the $car variable
does in fact exist.
This begs the question of how to really wipe variables from the face of the earth, or at least your Perl script. Simple.
$car ="Porsche 911";
$aircraft="G-BBNX";
&look;
undef $car; # this undefines $car
&look;
sub look {
print "Car :$car: Aircraft:$aircraft:\n";
print "Aircraft exists !\n" if $aircraft;
print "Car exists !\n" if defined $car;
}
This variable $car is eradicated, deleted,
killed, destroyed.
And now for something completely different....
