deseperatly seeking a regular expressions shuffle algorithm

[Antoine Beugnard]

I am seeking an algorithm that calculates the regular expression
resulting from the shuffle of two others.

example : (@ denotes the shuffle operation)
a @ b = a.b + b.a
a* @ x.y.z = a*.x.a*.y.a*.z.a*

The main problems are related to:
- the * operation defined as a closure...
a* = null + a + a.a + a.a.a + a.a.a.a + ...

- the nested structure of regular expressions
((a.b)*.((c.(d)*.e)* + u))...

I'll be pleased to receive any information related to such an algorithm,
and to transmit it to anybody interested in.

My e-mail address is

beug...@enstb.enst-bretagne.fr

Thank you.