Expression input
================
There are two forms of expression input. Both ignore leading
whitespace. The string argument to `eval()' must have the following
form:
eval_input: expression_list NEWLINE*
The input line read by `input()' must have the following form:
input_input: expression_list NEWLINE
Note: to read `raw' input line without interpretation, you can use the
built-in function `raw_input()' or the `readline()' method of file
objects.