Read "Mushroom-Gatherers" at The Eldritch Dark:
This poem from Clark Ashton Smith (CAS) presents something of an inversion of the usual "rules" of the haiku form in English, which typically uses a pattern of three lines of five, seven, and five syllables.
In "Mushroom-Gatherers", CAS instead uses five, five, and seven syllables. This works very well rhythmically, since the pace of reading resembles that of a limerick, where pairs of short lines lead into a longer closing line that provides the humorous "payoff" (see for example the many limericks authored by Edward Lear).
This is one of the reasons that I find a close study of CAS' poetry to be so rewarding: he was an artist that respected established poetic forms, but freely adapted those structures to suit his own needs, often with quite remarkable results.