>Can anyone explain me this (1.90.355) ?
This is expected behavior, and not a bug.
Basically, "==" is the "always exact" equal comparison operator, while "="
is the "inexact" equal comparison operator. The "inexact" not equal
comparison operators: "#", "<>", and "!=" behave the same as ".not. =", or
the opposite of the "inexact" equal comparison operator.
The "==" comparison is independent of the "Set Exact" setting, while all
other also depend on that setting.
If an inexact comparison is made, the (string) value on the left side of
the operator is tested only for the length of the (string) value on the
right side of the operator, so all strings are equal to an empty string,
while empty strings are only equal to other empty strings.
RTFM on "SET EXACT" for more details on this.
Hope that helps,