shmread id, var, pos, size
Reads from the shared memory segment id starting at
position pos for size size (by attaching to it, copying out, and
detaching from it). var must be a variable that will hold the data
read. The function returns true if successful, or false if there is
an error. On error, it puts the error code into $!. This
function is available only on machines supporting System V IPC.