They must be working abroad.
They may be working abroad.
They might be working abroad.
They can’t be working abroad.
They must have worked abroad.
They may have worked abroad.
They might have worked abroad.
They can’t have worked abroad.
He must be at work.
He must have been at work.
He may be at work.
He may have been at work.
He might be at work.
He might have been at work.
He can’t be at work.
He can’t have been at work.