There was a problem where the body of a for loop was treated like a
function and got an entirely new environment. This meant that you could
not, for instance, modify a variable in a loop and keep the changed
value after the loop finished executing.

Also, for consistency, switch to storing only fully evaluated values in
the environment.

^ matches the beginning of every line. Given the string
function() {
}
using /^\{/ will match the final } because it's at the beginning of the
line