<number> = '0'|..|'9'
<symbol> = 'a'|..|'z'|'A'|..|'Z'
<ten> = <symbol><symbol><symbol><symbol><symbol><symbol><symbol><symbol><symbol><symbol>
<five_less> = <symbol> | <symbol><symbol> | <symbol><symbol><symbol> | <symbol><symbol><symbol><symbol>
<six_less> = <five_less> | <symbol><symbol><symbol><symbol><symbol>
<eleven_less> = <six_less> | <six_less><six_less>
<start> = <ten><ten>
<end> = <eleven_less> | <eleven_less><eleven_less> | <eleven_less><eleven_less><eleven_less>
<letters> = <start>|<start><end>
<var_name> = <number> | '$' | '_' | <letters>