Start with "STAIN".
The letters "S", "T", "A", and "N" are not in the final word. "I" is in the correct position.
Use the following regular expression:
$ grep -P '^[^stan][^stan][^stan]i[^stan]$' /usr/share/dict/words
Choose "MOVIE":
The letters "M", "O", "V", and "E" are not in the finial word.
Add those hints to the current regular expression
$ grep -P '^[^movestan][^movestan][^movestan]i[^movestan]$' /usr/share/dict/words
Choose "FLUID":
The letters "F", "U", and "D" are not in the final word. The letter "L" is in the wrong position.
Add those hints to the currewnt regular expression:
grep -P '^[^fudmovestan][^fludmovestan][^fudmovestan]i[^fudmovestan]$' /usr/share/dict/words | grep l
Choose "LYRIC":
We won.