exit

exit EXPR

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.