All commands start with a '\'.  The following commands are defined:
 \help, \h, \?   - This help
 \exit, \quit    - Exit the program
 \radix          - Display the current radix (base)
 \radix <num>    - Set the radix to anything between 2 and 36 (inclusive)
 \scale          - Display the current scale
 \scale <num>    - Set the current scale
 \vars           - List all defined variables

All variables must prefixed with a $ but otherwise can be used anywhere a
number can be used.  To assign a variable use =, i.e.:
  $amnt = $rate * 144000.09

When using a radix greater than 10 all extended digits are lowercase letters
starting with 'a'.  Upper case is not currently supported.

All numeric command parameters (i.e. \scale, \radix) are in base 10 no
matter what radix is currently set.  These are also displayed in base 10
at all times.

Changing the radix always clears all variables.

Every result that is provided is placed into the variable $ans, which makes
running totals or reusing values without calculating them again easy, e.g.

552*0.01
5.52
$ans + 101
106.52