VMS Help CMS, REMOVE, GROUP, Qualifiers, /IF_PRESENT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Directs CMS to remove group-expression1 only if it belongs to
    group-expression2. If group-expression1 does not belong to group-
    expression2, CMS takes no action and does not return an error.
    When you use wildcard characters or a comma list in the group
    name, /IF_PRESENT is the default.