Towards a change of variable formula for "hypergeometrization"

We are going to study properties of “hypergeometrization” – an operator which act on analytic functions near the origin by inserting two Pochhammer symbols into their Taylor series. In essence, this operator maps elementary function into hypergeometric. The main goal is to produce number of “change of variable” formulas for this operator which, in turn, can be used to derive great number of transform for multivariate hypergeometric functions.