help please

[keshav prabhakar]

Hello all,
        Can someone please help me in understanding the help text when i
take the mouse pointer to the text box next to 'Execute' filter in the
'Customize Entries' screen.
The help text says:
    "    ... program with parameters to execute on match. The following
variables atre defined:
                %F: absolute path to file [=$XLM_FILE]

                %H: helptext of entry [=$XLM_HELP]
                    ...........
                    ...........
                otherwise use like usual command and command line... "

                Yes. i could execute my C program by writing the
executable file name in the text box. But I couldn't understand the
first part of the text in which "variables %F, %H, %L, %M, %N "
are         explained.
                Will someone please tell me how to use them ?
regards,
keshav