There are three youngsters having trouble with what he/she wants, what he/she needs (to follow the call), and the call itself. Or being confused with the difference between what they truly want and the temptation.
Peter. A Jesuit seminarian. Who wants to leave the seminary as he feels that following the call is not the life he wants to pursuit and is sent to Seaside, a soup kitchen at Alabama Gulf coast by Father Tew. At Seaside, he meets Jill and his confusion gets even worse. He is thought to have what it takes to be a priest, which would be the empathy, the sympathy and the leadership as a shepherd. However, he is not sure if he wants to become a priest.
Jill. A beautiful and charming volunteer working at Seaside. She is strong inside and believes joining Peace corps and working in Africa is what she needs to follow her path and truly what she wants to do. However, she has been rejected since Peace corps does not need what she has, a English teacher.
Gilbert. A fellow Jesuit seminarian of Peter's. He comes to Seaside with Peter and has no doubt that he wants to follow the call although he has not thought of what he needs to follow it.
The film shows calmly their journey to make their decision with no exaggeration.
It seems that the number 3 is key number in this film.
Peter's feet are growing and he needs new shoes three times. Jill has been rejected by the Peace corps working for Africa three times. Peter has three mentors guiding him, Fathers Bahnke, Tew and McIlhenny. Finally, life's equation has three variables, which are what he wants, what he needs, and the call (what he truly wants and needs). The word "salubrious" means the good balance between three variables in the film. When Peter made his choice, he told Jill he was salubrious.
When Jill accepts the different offer from the Peace Corps, Africa is revealed as a temptation. Jill has been distracted by serving "in Africa" although she has known what she wanted and what she needed. What she truly wanted was helping the people. She has the skill to help the people and finds out where she is needed eventually.
And then, Gilbert. This poor boy does not have what he needs to follow his call, "being a priest". Being a priest is not just serving the God. Rather, it is serving the people. When he learnt that he did not have what he needed to be what he truly wanted to be, he got frustrated and reached his own conclusion. His decision, of course, needs the huge courage as well. It would've been nice to see the details how Gilbert felt and made his own choice.
The Peter's shoes would be the metaphor of his call. Growing feet means Peter's spiritual growth. He thought the seminary was not for him and took off his shoes as soon as he arrived at Seaside. He initially thought he probably would like to strangle the needy and could not find out a pair of shoes for him from donations. He felt Father Bahnke did not see his agony and understand him. So he threw away the shoes Father Bahnke bought him. As St. Peter denied Jesus three times, Peter threw away his shoes three times. And then, he wanted to keep the shoes Jill got him and felt salubrious. I don't think this means Peter wants to be with Jill. Rather than that, he learns and accepts his calls from the relationship with Jill and Jill's determination, who has the similar conflict between want and need. When he was caged and slept in the cooler in the darkness, Jill was the one who woke him up and opened the door with daylight. With her, he met Father McIlhenny and saw the retirement of the elderly. Peter got the chances to see the frustration of whom were forcefully extracted from their duty as they were judged too old to serve by "Church", not by their own will. These may mean that Jill is the indispensable catalyst/ distraction/ helper for his spiritual maturity. Thus, although the film itself opens the end, I feel that Peter would like to continue the novice to follow his call whatever his answer is to Father Tew's question, "what are you gonna do, young man?", if he stays at Seaside or goes with Jill.
Going back to the beginning, Murray Robinson, the director and the writer of this film, tried to give a hint that the Peter would get lost to distraction of all temptations and journey to find his path and his true-self and to learn to face the essence of things, showing Peter distracted by beautiful parrot and women's breasts. In addition, the slough of a snake may mean Peter's final freedom from all confusions as a snake sheds its skin to grow.