文字列の右から検索する Pos 関数。
function ReverseString(const S: string): string;
var
I, L: Integer;
begin
SetLength(Result, Length(S));
L := Length(S);
for I := 0 to L - 1 do
Result[L - I] := S[I + 1];
end;
function RPos(Substr: string; S: string): Integer;
begin
Result := Pos(ReverseString(Substr), ReverseString(S));
if Result <> 0 then Result := Length(S) - (Result - 1) - (Length(Substr) - 1);
end;