> - they're not really specified anywhere This doesn't make sense > - they allow you to mutate your data in weird ways (in particular, you can change variable

> - they're not really specified anywhere This doesn't make sense > - they allow you to mutate your data in weird ways (in particular, you can change variables dynamically by knowing the name of the variable, aka "variable variables"). There are a few ways to naively do this. The first and easiest I'd say is just to make a jump table of all the variables in scope. Take a hash of the string and access that. The hardest way is to optimize out this access. Check to see where all of the callers are and inline the function to make the string hard-baked in. After that you can simply replace $some_string() with string_contents(); and get 0 overhead. > - they use `eval` and similar dynamic constructs This is harder but eval is largely discouraged and mostly unused (I hope). It can still be supported by linking in the compiler at runtime and calling the compiler on the string passed. It's slow but would allow it to work. Alternatively you could also do the inlining optimization trick.