VMS Help DSR, DSR Commands, Conditional Commands  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The .IF, .IF NOT, .ELSE, and .ENDIF commands (also known as
    the conditional commands) cause portions of a DSR file to be
    processed or not processed, according to conditions that you
    specify. The commands refer to the /VARIANT qualifier that you
    specify on the DSR command line. (See also /DEBUG=CONDITIONALS
    and .VARIABLE.)

    Formats

      .IF  name

      .ELSE  name

      .IFNOT  name (or .IN name)

      .ENDIF  name (or .EI name)

1 - Parameter

 name

    A word that is common to the conditional commands that make up a
    single .IF or .IFNOT block of text.