Why did Priest change the spelling of some words in the "Verde" limerick?

A lady who lived on the Verde 1

Considered herself very perde, 2

Til once in a mirror 3

She saw herself clirror 4

As not only ugly but derde. 5

--Florence Priest

Limericks are intended to give entertainment by making the listeners laugh. Part of that is to make the end syllables rhyme. Additionally, the words themselves even without their meaning should sound like its making fun of the subject. It is for these reasons that the priest changes the spelling of some words.