[perl #127779] Inconsistency with non-int $k in “combinations” (combinations 2, 0.5)

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Code:
say combinations 2, 0.5

Result:
(())

Code:
say combinations 2, 1.5

Result:
This type cannot unbox to a native integer
  in block <unit> at -e line 1


These results are inconsistent. 0.5 cannot be unboxed to a native int too, but 
it is accepted. I think that both should result in the same error.