6. Solutions: Vowel harmony in Old English

Implement the morphological rule which adds an 'iy' phoneme to end of a singular noun like "f ow t". Call it "oldplural". It should work as follows:

      alias oldplural='sed "s/$/ iy/g"'
      echo "f ow t" | oldplural
    

We can now implement the "vowel harmony" phonological rule:

      alias vowelharmony='sed "s/\( ow \)\([a-z]*\)\( iy\)$/ ey \2 iy/"'
    

Can you apply the vowel harmony rule to the output of the old plural rule to turn the singular "f ow t" into the Old English plural "f ey t iy"?

      echo "f ow t" | oldplural | vowelharmony