In version 7 and later, REX no longer returns certain
theoretically-correct but redundant empty hits. For example,
searching for the expression "a*" against the data
"a" used to return two hits - "a" and "" (empty
string at the end of buffer); in version 7 only the first hit is
returned. More specifically, hits are skipped where the entire match
\F parts) is empty and adjacent to
the previous entire match.