=over =item $SYSTEM_FD_MAX =item $^F X<$^F> X<$SYSTEM_FD_MAX> The maximum system file descriptor, ordinarily 2. System file descriptors are passed to Ced processes, while higher file descriptors are not. Also, during an C, system file descriptors are preserved even if the C fails (ordinary file descriptors are closed before the C is attempted). The close-on-exec status of a file descriptor will be decided according to the value of C<$^F> when the corresponding file, pipe, or socket was opened, not the time of the C. =back