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

Others have answered the question about the meaning of $?.

I thought I would also mention that it is also possible to get help on Perl's special variables at the command prompt:

perldoc -v $?

Depending on your shell, you may need to escape the $.

perldoc -h