Normally it is not necessarily to do this directly, because it suffices to
use the implicit discarding behaviour of L</lex_next_chunk> and things
based on it. However, if a token stretches across multiple lines,
-and the lexing code has kept multiple lines of text in the buffer for
+and the lexing code has kept multiple lines of text in the buffer fof
that purpose, then after completion of the token it would be wise to
explicitly discard the now-unneeded earlier lines, to avoid future
multi-line tokens growing the buffer without bound.