Update comment in except.h

src/except.h

@@ -9,21 +9,26 @@
 * error checking was taking a substantial amount of the coding. These
 * function greatly simplify the task of checking errors.
 *
-* The main idea is that functions should return nil as its first return
+* The main idea is that functions should return nil as their first return
-* value when it finds an error, and return an error message (or value)
+* values when they find an error, and return an error message (or value)
 * following nil. In case of success, as long as the first value is not nil,
 * the other values don't matter.
 *
 * The idea is to nest function calls with the "try" function. This function
-* checks the first value, and calls "error" on the second if the first is
+* checks the first value, and, if it's falsy, wraps the second value in a
-* nil. Otherwise, it returns all values it received. 
+* table with metatable and calls "error" on it. Otherwise, it returns all
+* values it received. Basically, it works like the Lua "assert" function,
+* but it creates errors targeted specifically at "protect".
 *
-* The protect function returns a new function that behaves exactly like the
+* The "newtry" function is a factory for "try" functions that call a
-* function it receives, but the new function doesn't throw exceptions: it
+* finalizer in protected mode before calling "error".
-* returns nil followed by the error message instead.
 *
-* With these two function, it's easy to write functions that throw
+* The "protect" function returns a new function that behaves exactly like
-* exceptions on error, but that don't interrupt the user script. 
+* the function it receives, but the new function catches exceptions thrown
+* by "try" functions and returns nil followed by the error message instead.
+*
+* With these three functions, it's easy to write functions that throw
+* exceptions on error, but that don't interrupt the user script.
 \*=========================================================================*/
 
 #include "lua.h"