is a sentence boundary.
There are two ways to divide sentences. The first assigns all
inter-sentence whitespace/control/format chars to some sentence,
so all chars are in some sentence; @is_sentence_boundary denotes
the boundaries there. The second way doesn't assign
between-sentence spaces, etc. to any sentence, so
@is_sentence_start/@is_sentence_end mark the boundaries of those sentences.
is a sentence boundary. There are two ways to divide sentences. The first assigns all inter-sentence whitespace/control/format chars to some sentence, so all chars are in some sentence; @is_sentence_boundary denotes the boundaries there. The second way doesn't assign between-sentence spaces, etc. to any sentence, so @is_sentence_start/@is_sentence_end mark the boundaries of those sentences.