bisa ibu+ibu bisa bapak+bapak
bisa ibu ibu bisa bapak bapak .
b i s a WORD_BOUNDARY i b u WORD_BOUNDARY i b u WORD_BOUNDARY b i s a WORD_BOUNDARY b a p a k WORD_BOUNDARY b a p a k WORD_BOUNDARY
b i s a WORD_BOUNDARY i b u WORD_BOUNDARY i b u WORD_BOUNDARY b i s a WORD_BOUNDARY b a p a k WORD_BOUNDARY b a p a k WORD_BOUNDARY . WORD_BOUNDARY