I could regret you could regret she could regret we could regret you could regret they could regret
V-ing form
I could be regreting you could be regreting she could be regreting we could be regreting you could be regreting they could be regreting
Perfect
I could have regreted you could have regreted she 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 she 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 she 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 she 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 she 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 she 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 she regret? could we regret? could you regret? could they regret?
V-ing form
could I be regreting? could you be regreting? could she be regreting? could we be regreting? could you be regreting? could they be regreting?
Perfect
could I have regreted? could you have regreted? could she 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 she 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 she 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 she 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 she 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 she have been regreting? couldn't we have been regreting? couldn't you have been regreting? couldn't they have been regreting?