In "Mother-of-Pearl," the strongest of the three new one-act plays by Robert Perring now playing at the Vault, the main character, Kay, earns her living as a chick-sexer in a poultry factory, a job that involves determining the sex of chicks and separating them accordingly. It's a little-known profession, but the kind of detail that characterizes this collection of plays, gathered under the title "Hometown Blues." Perring's characters are people like waitresses and unemployed construction workers, poor and uneducated, intended, one suspects, to represent the salt of the earth.

Unfortunately most of them are also stereotypes, echoes of television standards. In "Mother-of-Pearl," however, Perring shows that he can use a cliche' -- the whore with a heart of gold -- and make her real, aided greatly by a finely detailed performance by Bonne Brown Smith as the good-time girl who flaunts small-town convention. Kay works hard and supports her brother, a silent Vietnam vet who reads throughout the play. She also plays hard, picking up men at the local tavern when she feels like it and doing a valiant job of ignoring the gossip that follows. She is approached by the son of her long-dead first love (a nicely awkward performance by Robert Hicks), who asks her to show him the ropes, as it were, and after rather brief soul-searching she agrees.

"Cookies' Breakup" and "Twilight" are vignettes rather than plays. The actors, who include the author as the unemployed construction worker/sometime dope dealer in "Cookies' Breakup," are caught up in phony accents and imitative interpretations, although Lucy Brightman as a long-suffering Appalachian mother is sweetly effective.

HOMETOWN BLUES. By Robert Perring. Produced by the Source Theatre Co., directed by Lucy Brightman and Robert Perring, lighting by Lea Hart, costumes by Erica Kane; with Robert Perring, Theresa Aceves, Dexter Cannon, Bonne Brown Smith, Mary Stetina, Richard Hicks and Lucy Brightman. At the Vault through Nov. 22.