Implements the fcntl(2) function. You'll probably have to say
use Fcntl;
first to get the correct constant definitions. Argument processing and value returned work just like ioctl
below. For example:
use Fcntl;
my $flags = fcntl($filehandle, F_GETFL, 0)
or die "Can't fcntl F_GETFL: $!";
You don't have to check for