/sys$common/syshlp/helplib.hlb ON  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Performs a specified action when a command or program executed
    within a command procedure encounters an error condition or
    is interrupted by Ctrl/Y. The specified actions are performed
    only if the command interpreter is enabled for error checking or
    Ctrl/Y interrupts (the default conditions). Use the ON command
    only in a command procedure.

    Format

      ON  condition THEN [$] command

  Additional Information (explode) :

• Parameters
• Examples