A further postilla might be that they are rules without a fixed meaning. They do have a meaning, but this varies with time and according to the one who performs it (or, one might add, attends it).
From a study of Marion Rastelli, published in 2005 in Words and Deeds:
In their study on the Jaina pūjā, Caroline Humphrey and James Laidlaw have shown that ritual acts have no meaning that is intrinsic to them (Humphrey and Laidlay 1994: esp. 5, 35, 41). There is no immediate correlation between the external appearance of a ritual and the meaning that is attributed to it. From the observation of a ritual action one cannot infer the meaning being ascribed to it.
This remark could end many discussions on the interpretation of Vedic rituals (was the Soma-offering initially meant to propitiate rain? Is it a fertility rite? and so on). However, one might suggest that this view only regards rituals as they are observed and that it is indeed possible to speculate about their original meaning in history.
A further consequence of Humphrey and Laidlaw's point is as follows:
If the meanings attributed to a ritual and the intentions being pursued are independent from the outer form of a ritual, the meanings and the performer's intentions can change without transforming the ritual itself.In other words, a worshipper of a personal God may perform the same ritual a monist is performing, although attributing to it a very different meaning. One might object, again, that phenomenologically there might be huge differences in the intentions of the performers, but that these differences can be understood historically and that it is not the case that any ritual means everything, but rather that every ritual has an history and, hence, a historical stratification of meanings, partly alternative to each other.
(Rastelli 2005, p. 115)
What do you think? And how close are Staal's and Humphrey and Laidlaw's theses?