  < 1 >

  < 2 >

(->> (s/split book #"\s+") ; <3>
     (filter primary-colors)
     frequencies)
  { " red " 87 , " blue " 64 , " green " 38 }

  < 4 >
     (map s/lower-case)
     (filter primary-colors)
     frequencies)
  { " red " 89 , " blue " 64 , " green " 38 }
 <3>
  < 1 >

  < 2 >

     (filter primary-colors)
     frequencies)
  { " red " 87 , " blue " 64 , " green " 38 }

  < 4 >
     (map s/lower-case)
     (filter primary-colors)
     frequencies)
  { " red " 89 , " blue " 64 , " green " 38 }