Description

   The setenv function inserts or resets the environment variable
   name in the current environment list. If the variable name does
   not exist in the list, it is inserted with the value argument. If
   the variable does exist, the overwrite argument is tested. When
   the overwrite argument value is:

   o  0 then the variable is not reset.

   o  1 then the variable is reset to value.

                                  NOTE

      Do not use the setenv, getenv, and putenv functions to
      manipulate symbols and logicals. Instead, use the OpenVMS
      library calls lib$set_logical, lib$get_logical, lib$set_
      symbol, and lib$get_symbol. The *env functions deliberately
      provide UNIX behavior, and are not a substitute for these
      OpenVMS runtime library calls.

      OpenVMS DCL symbols, not logical names, are the closest
      analog to environment variables on UNIX systems. While
      getenv is a mechanism to retrieve either a logical name
      or a symbol, it maintains an internal cache of values for
      use with setenv and subsequent getenv calls. The setenv
      function does not write or create DCL symbols or OpenVMS
      logical names.

      This is consistent with UNIX behavior. On UNIX systems,
      setenv does not change or create any symbols that will be
      visible in the shell after the program exits.