I am generating simple SVG diagrams by using sed find and replace on some text input. However, I need a more sophisticated **find and replace operation involving simple math**, to alter certain X and Y values.

E.g. I need to multiply all Y values by a factor of 0.5 or 0.2 or 0.

Because of how I want this to work, it cannot be achieved with a transform operation within the SVG.\*

I just need to be able to find, say, all instances of `([0-9.]*)VERT` (in sed speak) and replace with the mathematical result of `\1` multiplied by the constant I choose.