What does a dollar sign followed by a question mark mean in Perl?

Question

In the following in Perl script:

$a=apple
$b=orange

if ($?==0) {
  # do something
}

What does $? mean here?

Answer 1

$?, along with all the other "magic" variables, is documented in the perlvar section of the Perl manpages. If you don't actually have a Unix-like setup with the man command, you should also be able to Google for man perlvar.