Grammar dangling;
Parser

f = e 
	; //1alt1 | e '2' '3' ;
e = '0' |
	'1' e | '1' e '2' ; //alt1 '1' e | '1' e x ; //alt2 '1' e y ; 
x = '2' ;
y = x | ;

/*
1102 -> f[ e[ '1' e[ '1' e['0'] '2' ] ] ]
1102 -> f[ e[ '1' e[ '1' e['0'] ] '2' ] ]
11022 -> f[ e[ '1' e[ '1' e['0'] '2' ] '2' ] ]
11023 -> f[ e[ '1' e[ '1' e['0'] ] ] '2' '3' ]
*/