if input to the perl program is ' ( p * ((a+b) * (c+d))) + q ' it shuld give the output as ' pac + pad + pbc + pbd + q ' .can anyone suggest a way to do this ?
Perl doesn't support that out-of-the-box, but maybe this can help you: Math::Symbolic - Symbolic calculations - search.cpan.org (First & Third result when searching for "perl symbolic math")
Thanks Pludi for replying...But it didn help.Can anyone suggest a metho may b by pattern matching or something
If it were for just that one specific pattern it would be possible, but I suspect the user input can be any number of varying combinations of math expressions, in which case trying to convert them to some other format needs a much more thought out approach.
actually, a lexicographical parser is required. then, some sort of commonizing engine.
i'll build it for a fee. 
I don't think its "required" if the input can be limited to something reasonable. Not that I would want to try and code such a parser myself even for a limited set of equations.
Of course a lexicographical parser would be a great solution if money and time were no problem. 
As others noted - this has the potential to be hellishly complex.
you could write a simple perl frontend to pari using one of it's interfaces, if you have to use perl. Pari interprets algebraic statements and then can work with them.
http://clisp.sourceforge.net/impnotes/pari.html
Ya u got it rite.Its not just for one pattern.The user input can be any number of variying combinations of math expressions.