I wanted to demonstrate that linear regressions are not just for finding straights lines that fit a set of points but also is more general. For this I wrote, in part, this trivial function:

randomRow[] := Module[{x, col}, 
   x = RandomReal[1];
   col = {1.0, x, x^2, x^3, x^4};
   col];

I got the syntax error that more input was needed. When I deleted and reentered the col = {} line, the error disappeared. Apparently, I must have entered some unprintable characters which caused the error.

Is there a way to show these "illegal" characters in the notebook so I can fix the problem without resorting to retyping an entire notebook?