my $pid = fork;
if ($pid) {
    # Parent.
} elsif (defined $pid) {
    # Child.
    # Don't forget to let it exit.
} else {
    # Error.
}

##</code><code>##

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$