I could regret you could regret he could regret we could regret you could regret they could regret
V-ing form
I could be regreting you could be regreting he could be regreting we could be regreting you could be regreting they could be regreting
Perfect
I could have regreted you could have regreted he could have regreted we could have regreted you could have regreted they could have regreted
V-ing perfect
I could have been regreting you could have been regreting he could have been regreting we could have been regreting you could have been regreting they could have been regreting
Negation
Simple form
I couldn't regret you couldn't regret he couldn't regret we couldn't regret you couldn't regret they couldn't regret
V-ing form
I couldn't be regreting you couldn't be regreting he couldn't be regreting we couldn't be regreting you couldn't be regreting they couldn't be regreting
Perfect
I couldn't have regreted you couldn't have regreted he couldn't have regreted we couldn't have regreted you couldn't have regreted they couldn't have regreted
V-ing perfect
I couldn't have been regreting you couldn't have been regreting he couldn't have been regreting we couldn't have been regreting you couldn't have been regreting they couldn't have been regreting
Interrogative form
Simple form
could I regret? could you regret? could he regret? could we regret? could you regret? could they regret?
V-ing form
could I be regreting? could you be regreting? could he be regreting? could we be regreting? could you be regreting? could they be regreting?
Perfect
could I have regreted? could you have regreted? could he have regreted? could we have regreted? could you have regreted? could they have regreted?
V-ing perfect
could I have been regreting? could you have been regreting? could he have been regreting? could we have been regreting? could you have been regreting? could they have been regreting?
Interro-negative form
Simple form
couldn't I regret? couldn't you regret? couldn't he regret? couldn't we regret? couldn't you regret? couldn't they regret?
V-ing form
couldn't I be regreting? couldn't you be regreting? couldn't he be regreting? couldn't we be regreting? couldn't you be regreting? couldn't they be regreting?
Perfect
couldn't I have regreted? couldn't you have regreted? couldn't he have regreted? couldn't we have regreted? couldn't you have regreted? couldn't they have regreted?
V-ing perfect
couldn't I have been regreting? couldn't you have been regreting? couldn't he have been regreting? couldn't we have been regreting? couldn't you have been regreting? couldn't they have been regreting?