Once a year a festival is held at the caves (which, by the way, is banned in India) in which many of the Hindus pierce their skin with fish hooks tied to weights either to show devotion or to ask for forgiveness for a sin committed during the past year. They march from the main Hindu temple in Kuala Lumpur to the cave where they say a prayer asking for forgiveness or expressing devotion. Then they throw off the hooks and weights, symbolic of losing the heavy weight of their sins.
This is indeed a rite of penitence and quest for forgiveness of sins.
(Inserting fish hooks as I type.)
Lol!