Here is a simple use of parsed and standard Streaming segmentation devices to parse a file in which groups of numbers are separated by blank lines. Such a problem of 'nesting streams' is described in the conduit context in this StackOverflow question

-- $ cat nums.txt
-- 1
-- 2
-- 3
--
-- 4
-- 5
-- 6
--
-- 7
-- 8

We will sum the groups and stream the results to standard output:

import Streaming
import qualified Streaming.Prelude as S
import qualified Data.ByteString.Streaming.Char8 as Q
import qualified Data.Attoparsec.ByteString.Char8 as A
import qualified Data.Attoparsec.ByteString.Streaming as A
import Data.Function ((&))

main = Q.getContents           -- raw bytes
       & A.parsed lineParser   -- stream of parsed `Maybe Int`s; blank lines are `Nothing`
       & void                  -- drop any unparsed nonsense at the end
       & S.split Nothing       -- split on blank lines
       & S.maps S.concat       -- keep `Just x` values in the sub-streams (cp. catMaybes)
       & S.mapped S.sum        -- sum each substream
       & S.print               -- stream results to stdout

lineParser = Just <$> A.scientific <* A.endOfLine <|> Nothing <$ A.endOfLine

-- $ cat nums.txt | ./atto
-- 6.0
-- 15.0
-- 15.0