From toot https://mspsocial.net/@earthtopus/110325319793286894
https://federation.p1k3.com/@earthtopus@mspsocial.net/110325319839116047 -

    @brennen oh, OK.  I want a thesaurus mapping English headwords to
    Anglish-only synonyms.

    Here (https://www.gutenberg.org/dirs/3/2/0/3202/files/mthesaur.txt) is a 24
    MB file comprising a thesaurus of line-initial "$headword" followed by many
    substrings of ",$synonym".

    I want to preserve all headwords intact while removing all ",$synonym"
    substrings that contain Es.  I think that's all of it.

The mthesaur.txt here is a 2-line sample of the full file.