"The Eddie Capra Mysteries," as unveiled in a special two-hour premiere on NBC tonight, looms as a highly presentable TV trifle and an engaging revision of "Perry Mason" - smuttied up a bit for the sleazy '70s, of course.

Like Mason," the "Capra" show, at 9 tonight on Channel 4 (henceforth at 10) is an attractively produced and serviceably scripted ritual. There are five parts to this rite, the display of the victim-to-be and parade of suspects; the murder itself; the entry of the sleuth (lawyer Capra) into the case; the investigation, and finally, the convocation of suspects, summoned by the sleuth so he can name one of them culprit.

It worked well for fatso and it could work for Eddie, which is not to suggest that he and his crew of crime-solvers approach the sublime communal charisma of Mason, Paul Drake and Della Street. Let's not expect mircales. Still, maverick Capra, as played by Vincent Baggetta, and his saucey girlfriend Lacey, as played by Wendy Philips, are attractive and personable, especially in their scenes together.

NBC is supposed to be as sex-free as an Ivory Snow box this season, but Eddie and Lacey almost live together - their apartments are mere steps apart, though Lacey has a little girl by a previous marriage who sometimes interrupts the pair at crucial romantic junctures.

In addition, the murder mystery plot has its dark and sickie undertones. "You don't suppose the killer was into necrophilia?" Lacey asks at one point. There is much talk of "sleeping together"; one of the female suspects says of the deceased, "I couldn't kill him any more than I could sleep with him."

The victim this time, played with his usual superbly snarling imperiousness by Robert Vaughn, is a rotten malicious millionaire who has a life-size model of King Arthur's sword-in-the-stone sitting in front of his mansion. The way he alone can pull out the sword is part of the mystery, so Capra constructs a smaller model of clay and toys with it at the dinner table.

Lacey watches him for a moment as he pushes the sword in and out of the clay and then says, "I wish you wouldn't do that." He asks, "Do what?" She says, "Never mind." There is something appealingly adult about this little burst of naughty innuendo, at least when compared to the cutesy leers of most TV shows that bring up the subject of sex, and the scene is very deftly played by Baggetta and Phillips.

Writer-producer Peter S. Fischer gave Capra a whole catalogue full of eccentricities that establish him as a rogue and a loner in the tired tradition of TV gumshoes from Baretta to Rockford, but Baggetta somehow turns the ingredients into a believable blowhard, though it would be nice if Capra could be allowed some other favorite aria besides Verdi's "La donn'e mobile," which he plays repeatedly on a taps cassette.

Director James Frawley animates the tale with about as much style as one can find in a TV movie, and the cast of guest suspects includes Stella Stevens, Lois Nettleton, George Hamilton, John Considine and Robert Walker. Of course it's all a trumped-up affair, but at least the trumping is competent and persuasively smart-alecky.