Update colum in dataset based on comparison of 2 other columns

[VCucu]

have

c1 c2 

aa bb

cc cc

aa aa

want

c1 c2 eval

aa bb NOK

cc cc OK

aa aa OK

can you do this with a proc sql ?

thank you

[Kurt_Bremser]

case
  when c1 = c2
  then 'OK'
  else 'NOK'
end as eval