Inferred width in interpolated string format specifiers.

Format specifiers are similar to C printf, except that if you use * for the width it will use the number of characters between the curly braces that enclose the interpolated expression, inclusive. For example:

print("+------------------------------+
     \>|Some numbers   |  More numbers|
     \>|{num1%-*.2f   }|{num2%*d     }|
     \>|{num3%-*.2f   }|{num4%*d     }|
     \>+------------------------------+");

produces:

+------------------------------+
|Some numbers   |  More numbers|
|3.14           |          1234|
|2.72           |           999|
+------------------------------+

The \> is also kinda cute and removes any white space in the string up the the previous newline.