3 skinless, boneless chicken breast halves - cut into 1/2 inch strips
2 tablespoons ketchup
2 tablespoons olive oil
1 1/2 teaspoons white wine vinegar
1 teaspoon dried oregano
1 teaspoon mustard powder
1 1/2 teaspoons curry powder, or to taste
4 pita breads, cut in half
2 cups mixed salad greens
1 cup plain yogurt