"Tonight, I'd like to try something a little different," says Shirley MacLaine at the beginning of her latest CBS special. "Actually, I'd like to try something different every night. But this time, you get to watch."

Twinkle, twinkle, twinkle! And industrial-strength twinkle at that. MacLaine has slipped into her pixie boots again. "Shirley MacLaine: Illusions," at 9 on Channel 9, might better have been titled "Shirley MacLaine: Delusions," of grandeur, perhaps, or just aggravated cuteness. This chapter in the seven middle ages of Shirley MacLaine was obviously deemed so humdrum by network executives that they dumped it into the arid viewing climes of summer. Bloom like an oasis it does not.

The theme of the show is that dog-tired one about the difference between illusion and reality (every lousy rock group in the world has recorded at least one meandering ditty on the subject). For some reason, this particular essay opens with a look at the wonderful world of hookers, as MacLaine reprises her roles in the flop movie musical "Sweet Charity" and in the Billy Wilder comedy "Irma La Douce." Hookers are harder to avoid on television than they are at the corner of 14th and L.

MacLaine apparently does not like sharing the screen with others. Director Don Mischer dutifully zooms in on Zee Big Cheese during ensemble dance routines. Then, through the magic of television, Shirley is able to share the screen with . . . herself! It's every actor's dream. After this split-screen gambit wilts, an honest-to-goodness guest star materializes, the great Gregory Hines (mit earring, alas) and the two of them do an inconsequential hat medley.

Soon Hines is gone, the two Shirleys have returned, but the program does wander off into somewhat enchanted territory, as MacLaine electronically melts into a blue-and-green painting and then romps through a series of video-trick fantasies choreographed by Alan Johnson. This is followed by an embarrassingly precious dramatic set-piece to the tune of me-me-me; "Who has the power to see me through? I do! I do! I do! I do! I do!" MacLaine shouts, to the cheers of the studio audience.

And finally, a word or two from MacLaine about her "hopes and dreams for the future of mankind," as she sings an unlikely medley of Oscar Hammerstein's "Cockeyed Optimist" and John Lennon's "Imagine," a fitting finale perhaps for a musical special as unimaginatively cockeyed as this one. Dinah Shore used to do more entertaining and enterprising shows than "Illusions," and she did one every week. The musical-variety "special" has fallen on very hard times indeed.