[xml] How can i do regexp operation?

[kalyanasundaram <s kalyanasundaram gmail com>]

Hi all,
  My job is right now, read the xml node element and update few
attribute and make another copy of the doc.

I have a node like this
<node val="S 100,164.44 D -199> 
even more complex i have it. I need to parse them and sometime i need to
add some value to that or subtract.

So manually i started parsing it. Now i feel it is difficult to write a
complete parser. Is there any regular expression support available in
libxml? Does xpath comes in help for this?

thanks for your help,
  -"kalyan"