Using regular expressions for left/right transformation

I am assuming this probably is not supported, but I thought I would ask anyways. 
I would like to create a left transformation that matches a regular expression or a specific concept. Specifically: "[0-9]+\s?(PL|NL|UL|ML|L)".

I am creating a language that deals with fluids. The syntax of the concept looks like this:

<integerLiteral><Vol unit> of <fluid Name>.

Users can optionally specify a volume of the fluid. So by default, the fluid concept has volume hidden. I have created a concept to hold volume components, but since volume begins with a integer(integerLiteral from base language), is there anyway to trigger a left transformation that matches the volume concept?

Thanks,

Chris