If you’ve ever had to parse strings in InstallShield’s InstallScript, you’d know that a few of InstallShield’s built-in String Functions might not be enough. Regular Expressions are a way to go, but unfortunatelly Acresso didn’t implement them (yet?) in their product.
This post from Acresso Community might have a solution for you (at least until Acresso will figure out a way to implement RegEx natively in their products).