"There once was a young man from Kent,
Whose cock was so long that it bent.
To save him the trouble,
He put it in double,
And instead of coming, he went."
See how the Limerick is composed?
The first, second, and fifth lines rhyme, and the rhyming refrain falls on the 3rd and 4th lines.
It even looks better in print when they're seperated this way.