The assembled pooh-bahs of Hollywood paid tribute to writer-director Billy Wilder the way porcupines are said to make love: very, very carefully. Despite the warning of Audrey Hepburn, who flew in from foreign parts to participate in tonight's presentation of the American Film Institute's Life Achievement Award, that "praise and sentiment might make him leave the room," the air was filled with the kind of decorous flattery that the man himself used to skewer so rigorously in his films.

Responsible for such classics as "Sunset Boulevard," "Some Like It Hot," "Stalag 17," "The Lost Weekend" and "Double Indemnity," Wilder (who will be 80 this summer) has done much to raise the barbed quip to a Hollywood art form. He once told an actor, "You have van Gogh's sw,-2 sk,2 ld,10 ear for music," advised Walter Matthau that "we're on the track of something absolutely mediocre," and sweet-talked his prospective wife with a tart "I'd worship the ground you walk on if you lived in a better neighborhood."

It was in anticipation of similar sallies that an assortment of stars who ranged from Sylvester Stallone to Jimmy Stewart, Ginger Rogers to Priscilla Presley, paid $500 a ticket for the Beverly Hills extravaganza. Even such notorious Hollywood homebodies as Steven Spielberg and Amy Irving and Hugh Hefner and his latest conquest turned out. They listened to the music of Nick Perito and the Life Achievement Award Orchestra, tentatively fingered miniature chocolate-covered Sunset Boulevard street signs, and soaked up an hour and three quarters of festivities that NBC will reduce to 60 minutes when it telecasts the event April 26.

Jack Lemmon, veteran of seven Wilder films, was the inevitable choice for master of ceremonies.

"He loves actors, don't get me wrong," Lemmon said of Wilder, "but some of us feel he is at times a tad demanding."

Lemmon then read off a rapid-fire list of performers who'd had heart attacks, left the business or suffered debilitating injuries after working with Wilder. "I cannot tell you," he concluded with deadpan finality, "how pleased I am to be here."

Equally grateful was Fred MacMurray, who spoke candidly of his fears about playing a smooth-talking killer in the 1944 "Double Indemnity," based on the James M. Cain novel.

"I had kind of an image," MacMurray explained. "I thought I would lose whatever friends I had, if any, so I told Billy, 'I'm sorry, I just can't do it.' But between you and me, it was really the first time I'd been offered a part which would require, in my mind, acting. The truth is, I really didn't think I could handle the part. But you know, I've made 85 pictures and most people remember 'Double Indemnity' best."

Aside from Lemmon, the actor most associated with Wilder is Walter Matthau, who allegedly once responded to one of the Vienna-born Wilder's accented monologues with a flat "You speak kinda funny. You from out of town?" Matthau's tribute started with the expected Wilder joke, and then moved on to somewhat more serious things, like Wilder's views on subtlety in film: " 'Of course, there must be subtleties. Just make sure you make them obvious.' He sees the world we all see, but he sees the worst in the best of us and the best in the worst of us, and he has the wit and talent and courage to tell us about it . . . In the world of Billy Wilder, the situation is definitely hopeless, but not serious."

The evening's wittiest remarks came from Wilder's longtime writing partner, I.A.L. Diamond, of whom the director once said, "Without him I'd be lost, like Abercrombie without Fitch." Referring to the films they had worked on, Diamond cracked, "This business has come a long way since then, but why should I depress you." He brought down the house with a recollection of a newspaper clipping Wilder recently showed him.

"It was an interview with the shah's son, who said his main ambition was to return to Iran and assume his father's throne, but failing that, he'd like to be a movie director," Diamond said. "There's hope for this industry yet."

Although some of the tributes from the older veterans of the Wilder wars sounded pro forma, younger performers who never had the chance to work with him spoke with surprising passion. Jessica Lange revealed that it was watching "Some Like It Hot" in a Paris theater that first made her want to act in movies, and Whoopi Goldberg, after pointing to her decorous outfit and saying, "I put this dress on for you," related a legendary Wilder story: Producer Samuel Goldwyn turned down his idea to do a biography of the great dancer Nijinsky because the man had ended up in a mental institution believing he was a horse. "My version," said Wilder, "will have a happy ending. We wind up showing him winning the Kentucky Derby."

After being introduced by AFI founder George Stevens as someone who "has been telling us the truth and making us laugh for nearly half a century," the bespectacled Wilder, looking like a stunned cherub, rose to speak. He told his own Goldwyn story, about how the producer had admonished him, "When are you going to learn you have to take the bitter with the sour," paid tribute to departed colleagues, especially director Ernst Lubitsch, "the one and only," and noted that with all the talent in the next world, "man, what a picture you could cast up there."

"I've been here for more than half a century, and I've watched Hollywood vacillate between despair and fear," Wilder said, launching into a dissertation about the industry's nervousness about new technology. "But even if they have 5 million screens from Albania to Zanzibar, there's one little detail. What about the software? Who will write it, who will direct it, who will act in it? . . . Relax, fellow picture makers. We are not expendable. The bigger they get, the more powerful we get. Theirs is the kingdom; ours is the power and the glory."

Wilder was followed by Lemmon, who said: "For the first time since I've known you, I'm going to get in the last word. Good night, Billy, and thank you."