... Doing isearch-forward-regexp against the line (note the "x"): "aaa aaaa aaaaaaaa aaaaa aaaaax aa" , via the regexp ...FIVE "a's") will match that *same* "aaaaaa aaa..." string (at least not for me!):...-w, put POINT somewhere before that "aaaaa"-string, and then, as above, do ..., it does match, but not that "aaaaaa..."-line, but rather the very one of...