arglist definition

[ | expr | param:=expr ][, ...]

A list of zero or more exprs that are assigned to the parameters of the procedure.
•A positional parameter may be skipped by omitting the expression. Only optional parameters may be skipped.
•Positional parameter assignment is done with expr. Each parameter is assigned in turn. By name parameter assignment may follow.
•By name parameter assignment is done with param:=expr. All following parameters must be assigned by name.