Each poem, said the man, must rhyme
lest it be worth less than a dime.
I think it is like presupposing
that lawns and gardens get a hosing
through rubber tubes, not from the sky
or, please recall the Lorelei,
her hair was golden, also long
she only sang one lovely song,
could it be true that, short of hair
Brunette or blond, we would not dare
refer to her as Lorelei?
And then, my friends, there is the pie,
one may pronounce that pies are round
their weight may be more than a pound
all pies are eaten from a plate
by humans, but consider, mate,
that bovine pies do not fulfill
exclusively this codicil!

So, use with care your black and white
because the darkness has no light,
yet night cannot be seen as dark
and dog is not the same as bark,
the secret to this puzzle is
be flexible, for Nature is!

Herbert Nehrlich

http://www.poemhunter.com/poem/a-poem-needs-no-rhyme-to-be/