VMS Help LBR Routines, LBR$GET_INDEX, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    LBR$GET_INDEX searches through the specified index for a key that
    matches the argument match_desc. Each time it finds a match, it
    calls the routine specified by the routine_name argument. If you
    do not specify the match_desc argument, it calls the routine for
    every key in the index.

    For example, if you call LBR$GET_INDEX with match_desc equal to
    TR* and index_number set to 1 (module name table), then LBR$GET_
    INDEX calls routine_name for each module whose name begins with
    TR.