Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could keen keen you could keen keen he could keen keen we could keen keen you could keen keen they could keen keen
V-ing form
I could be keen keening you could be keen keening he could be keen keening we could be keen keening you could be keen keening they could be keen keening
Perfect
I could have keen keened you could have keen keened he could have keen keened we could have keen keened you could have keen keened they could have keen keened
V-ing perfect
I could have been keen keening you could have been keen keening he could have been keen keening we could have been keen keening you could have been keen keening they could have been keen keening
Negation
Simple form
I couldn't keen keen you couldn't keen keen he couldn't keen keen we couldn't keen keen you couldn't keen keen they couldn't keen keen
V-ing form
I couldn't be keen keening you couldn't be keen keening he couldn't be keen keening we couldn't be keen keening you couldn't be keen keening they couldn't be keen keening
Perfect
I couldn't have keen keened you couldn't have keen keened he couldn't have keen keened we couldn't have keen keened you couldn't have keen keened they couldn't have keen keened
V-ing perfect
I couldn't have been keen keening you couldn't have been keen keening he couldn't have been keen keening we couldn't have been keen keening you couldn't have been keen keening they couldn't have been keen keening
Interrogative form
Simple form
could I keen keen? could you keen keen? could he keen keen? could we keen keen? could you keen keen? could they keen keen?
V-ing form
could I be keen keening? could you be keen keening? could he be keen keening? could we be keen keening? could you be keen keening? could they be keen keening?
Perfect
could I have keen keened? could you have keen keened? could he have keen keened? could we have keen keened? could you have keen keened? could they have keen keened?
V-ing perfect
could I have been keen keening? could you have been keen keening? could he have been keen keening? could we have been keen keening? could you have been keen keening? could they have been keen keening?
Interro-negative form
Simple form
couldn't I keen keen? couldn't you keen keen? couldn't he keen keen? couldn't we keen keen? couldn't you keen keen? couldn't they keen keen?
V-ing form
couldn't I be keen keening? couldn't you be keen keening? couldn't he be keen keening? couldn't we be keen keening? couldn't you be keen keening? couldn't they be keen keening?
Perfect
couldn't I have keen keened? couldn't you have keen keened? couldn't he have keen keened? couldn't we have keen keened? couldn't you have keen keened? couldn't they have keen keened?
V-ing perfect
couldn't I have been keen keening? couldn't you have been keen keening? couldn't he have been keen keening? couldn't we have been keen keening? couldn't you have been keen keening? couldn't they have been keen keening?