Shampoo bottle instructions

Anybody in computer science is familiar with the shampoo bottle instruction

Lather - Rinse - Repeat

that many of us use as an example of an infinite loop. On a hotel shampoo bottle recently I came across an example of another interesting instruction:

If seal is broken do not use

Of course, if the seal is not broken you cannot use the shampoo, so I guess this is an example of an always-negative logic statement...