John, I just tried your file exchange solution out of pure curiosity. Your guess is correct; it does score poorly. I also got the error "You may not use the command(s) builtin in your code" for the test cases. All I did was change only the first line to call the function and the variable names with no other checking. I'll do some real work on it now. :)
Test  Status  Code Input and Output 

1  Fail 
x0y0 = [2 5];
P = [0.5 3 5];
y_correct = 4.3093988461280149175163000679048;
tol = 5e13;
assert(abs(distance2polynomial(P,x0y0)y_correct) < tol)

2  Fail 
x0y0 = [pi, pi];
P = [10];
y_correct = 6.8584073464102067615373566167205;
tol = 7e13;
assert(abs(distance2polynomial(P,x0y0)y_correct) < tol)

3  Fail 
x0y0 = [0.25,50];
P = [1 2 3 4 5];
y_correct = 1.6470039192886012020234097061626;
tol = 5e13;
assert(abs(distance2polynomial(P,x0y0)y_correct) < tol)

4  Fail 
x0y0 = [3 3];
P = [2 1];
y_correct = 4.4721359549995793928183473374626;
tol = 5e13;
assert(abs(distance2polynomial(P,x0y0)y_correct) < tol)

5  Fail 
x0y0 = [0 5];
P = [1 0 1];
y_correct = 1.9364916731037084425896326998912;
tol = 2e13;
assert(abs(distance2polynomial(P,x0y0)y_correct) < tol)

6  Fail 
x0y0 = [2 5];
P = [0.5 3 5];
y_correct = 1.8901381949770695260066523338279;
tol = 2e13;
(abs(distance2polynomial(P,x0y0)y_correct) < tol)

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