Herbert Nehrlich - A Real Puzzle

It was a tiny little tag
and no one really would brag
about its size or form or shape,
it hid behind a light pink drape
and there it waited for the day
when they would innocently play
and then, in logical progression
unite and rupture, by compression
the symbol of sweet innocence
now relegated to past tense.
I ask you, folks, what can it be?
It isn't something one can see,
yet girls and boys and full-grown men
will talk about it, now and then.

Herbert Nehrlich

http://www.poemhunter.com/poem/a-real-puzzle/