[
  ~case sensitive
]

eof = -1
eol = '\n'

grammar
 -> [word...|eol...|string 1 | string 2]/..., eof

word
 -> "yes"   =printf("Input was yes\n");
 -> "no"    =printf("Input was no\n");

string 1
 -> 'a-n'... = printf("input was 'a-n'...\n");

string 2
 -> 'O-Z'... = printf("input was 'O-Z'...\n");