```uclid
module mutual_exclusion_protocol
{
  // Variables definition
  type pid_t = boolean;
  const p0 : pid_t = false;
  const p1 : pid_t = true;

  var s : pid_t;
  var y0 : boolean;
  var y1 : boolean;

  // Initial state
  init {
    s = p0;
    y0 = false;
    y1 = false;
  }

  // Transition relation
  next {
    case
      // Process P0 action
      :: true ->
        case
          // Noncritical section
          :: true ->
            y0' = true;
            s'  = p0;

          // Enter critical section
          :: (y1 = false || s != p0) ->
            y0' = false;
            s' = s;
        esac;

      // Process P1 action
      :: true ->
        case
          // Noncritical section
          :: true ->
            y1' = true;
            s'  = p1;

          // Enter critical section
          :: (y0 = false || s != p1) ->
            y1' = false;
            s' = s;
        esac;
    esac
  }

  // Safety property to check mutual exclusion
  // Check that both cannot be in the critical section simultaneously
  property mutual_exclusion {
    !((y0 = true && y1 = true) && (s = p0 && s = p1))
  }

  // Liveness property to ensure starvation freedom
  // Check that if one process wishes to enter critical section, it eventually does
  property starvation_freedom_P0 {
    always (eventually (y0 = true) -> eventually (s = p0 && y0 = false));
  }

  property starvation_freedom_P1 {
    always (eventually (y1 = true) -> eventually (s = p1 && y1 = false));
  }

  // Control procedure
  control {
    check;
    print_results;
  }
}
```
This fixes the syntax error in your original code. The `pid_t` type and its usage have been corrected, and the syntax and semantics were adapted to fit within UCLID5’s expected structure. The properties also have been adjusted to use proper logical operators to enforce mutual exclusion and starvation freedom correctly. Please try compiling this fixed version.