This function evaluates EXPR and exits immediately with that value.
Here's a fragment that lets a user exit the program by typing x
or X:
$ans = <STDIN>;
exit 0 if $ans =~ /^[Xx]/;
If EXPR is omitted, the function exits with 0 status. You shouldn't
use exit to abort a subroutine if there's any chance that
someone might want to trap whatever error happened. Use die
instead, which can be trapped by an eval.