What is the syntax for perform statement? | SAP-ABAP

 The perform statement is used to call a subroutine in a program.
The syntax of the perform statement is as follows:
 perform x) sub
              y) p of sub1 sub2 sub3...
                 [tables tab1 tab2 ...]
                 [using us1 us2 ...]
                 [changing ch1 ch2 ...]
 where:
sub, subl, sub2, sub3 - names of the subroutines.
p - It is a numeric variable.
x) and y) - These statements are mutually exclusive.
The following are the some of the restrictions of perform statement:
=>    tables, using, and changing can appear with either x) or y).
=>    The addition value() cannot be used with perform statement.