Is there a Guide or Reference for the Script Syntax?

Hi,

We're looking into replacing AutoCAD with Draftsight, I need some reference to help me understand all the variables in more advance Scripts, like this:

\\\$M=\\\$(if,\\\$(eq,\\\$(substr,\\\$(getvar,GetActCmd),1,4),GRIP),_STRETCH,^C^C_STRETCH)

I got the Customization Guide, but it doesn't show any of this, any feedback would be helpful.

Thanks.