Placeholders are syntactic character strings that hold the  place  of
  program language constructs.  When a placeholder name is expanded, it
  expands  to  either  an  actual  value  (terminal  node)  or  another
  construct  (nonterminal  node)  requiring further expansion (see also
  Topics "Tokens_and_Placeholders").

  The LSE commands used for the manipulation of placeholders are:

       DEFINE PLACEHOLDER name
             specifies placeholder characteristics for the current
             language.

       DELETE PLACEHOLDER name
             cancels the effect of a DEFINE PLACEHOLDER command.

       END DEFINE
             terminates a DEFINE command.

       ERASE PLACEHOLDER
             deletes the text of a selected placeholder.

       EXPAND
             expands the placeholder-name at the current cursor postion.

       EXTRACT PLACEHOLDER placeholder-name
             selects the definition of the named placeholder and formats
             it as a command.

       GOTO PLACEHOLDER
             moves the cursor to the next placeholder.

       SAVE ENVIRONMENT [file-spec]
             writes all user-defined placeholders to the specified file.

       SHOW PLACEHOLDER [name | * ]
             displays the characteristics of the specified placeholder.

       UNEXPAND
             reverses the effect of the last EXPAND command.