A variable that encapsulate internal parser state:
lexer


Creating a default lexer:
<lexer> ( text -- lexer )


A word to test of the end of input has been reached:
still-parsing? ( lexer -- ? )


A word to advance the lexer to the next line:
next-line ( lexer -- )


Two generic words to override the lexer's token boundary detection:
skip-blank ( lexer -- )

skip-word ( lexer -- )


Utility combinator:
with-lexer ( lexer quot -- newquot )