Library /sys$common/syshlp/dbg$help.hlb DEBUG, Built in Symbols, %LINE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    %LINE n is the debugger syntax for referring to line n in
    your program. You can qualify the line number with a path name
    specifying the containing module.

    Example:

    DBG> SET BREAK MODULENAME\%LINE 10

    The old syntax of %LINE MODULENAME\n is no longer accepted.