fork_join, fork_join_any, fork_join_none

Inside procedural block we use fork_join. It is used to make execution concurrenty inside procedural block. If there is no begin end inside fork_join, each statement is a process.
In Fork_Join_Any, all the processes starts simultaneously and join_any waits for any one process to complete.
Fork_Join_none, all processes start simultaneously and join_none does NOT WAIT for any process to complete.