A perverb (contraction of "perverse proverb") is a sentence that starts out like a well-known proverb or other expression, but ends in such an unexpected way that the listener is forced to back up and re-parse several words in order to get its sense. Examples:

• You can take a horse to water it down, but be sure to return it.
• Don't count your chickens will do it for you.
• Think before you were born you were already loved.
• While there is life better than while here?
• You can't teach an old dog would be better for your students.
• Time flies like to fly around clocks.

To be effective, a written perverb must have correct syntax, spelling, and punctuation, as in the "time flies" example above. Those that require a change in spelling or punctuation, like the "counting chickens" example above, may still qualify as "oral" perverbs.

The term perverb is also used in the weaker sense of any proverb that was modified to have an unexpected, dumb, amusing, or nonsensical ending, or the ending of another proverb — even if the changed version is no harder to parse than the original:

• A rolling stone gathers momentum.
• All that glitters is not dull.
• A penny saved is a penny indeed.
• Don't put the cart before the aardvark.