Here is the promised holiday competition. You are Clement Clarke Moore. You have read the line from ''Hamlet'' that says ''not a mouse stirring.'' You are convinced that you could work it into a few lines of jolly verse. Now we know what you finally wrote: 'Twas the night before Christmas, when all through the house Not a creature was stirring, not even a mouse.
However, you make several false starts, all in rhymed couplets but without the myth of Santa Claus, the reindeer, or maybe even the mouse. The only words your false starts share are '' 'Twas the night before Christmas when . . .'' Please send us just one of these false starts - no more than 10 lines, please.
As usual the address is The Home Forum Competition, The Christian Science Monitor, One Norway Street, Boston, Mass. 02115, and entries become the property of the Monitor. Those received as late as Jan. 12 (to allow for the seasonal mails) will be eligible for awards to be announced Feb. 6.