Many users appear to be confused by the notation used in the user manual to describe the syntax of procedures.  Eg:

  ADD FILES

     Per input file:
             /FILE={*,'FILE_NAME'}
             [/RENAME=(SRC_NAMES=TARGET_NAMES)...]
             [/IN=VAR_NAME]
             [/SORT]

     Once per command:
             [/BY VAR_LIST[({D|A})] [VAR_LIST[({D|A})]...]]
             [/DROP=VAR_LIST]
             [/KEEP=VAR_LIST]
             [/FIRST=VAR_NAME]
             [/LAST=VAR_NAME]
             [/MAP]

It is not obvious, to a non-computer scientist, what is to be interpreted literally, and what should not be.
Although there is a Section in Chapter 6 entitled "Backus-Naur Form" this does not explain, for example, that [...] indicates optional construction.  And anyway, most readers do not notice this section in the manual.