Mask with WDI to get data from several countries

hello all

I am successfully downloading inflation from WDI with rdb("WB","WDI","A-FP.CPI.TOTL.ZG-USA") but am unable to figure out how to use a mask to get inflation for all (or several) countries. rdb("WB","WDI","A-FP.CPI.TOTL.ZG-.") or rdb("WB","WDI","A-FP.CPI.TOTL.ZG-USA+DEU") will not work. And I tried every combination I could think of. I must be missing something incredibly stupid, but if anybody knows, much appreciated.

best, jack