i cloned https://github.com/rsdoiel/xlisp and it turns out that, although the original ast-walking xlisp was for the z80 under cp/m, this version is an r3rs scheme. the stripped executable is 303.6 kilobytes. historical versions of xlisp were easy to embed, and api.doc indicates that this is a priority for this version as well

amusingly, this xlisp package includes a tk interface—by embedding tcl

an earlier xlisp, i think for cp/m-86, is http://www.cpm.z80.de/download/xlisp.zip. it is written in c, about 2800 lines of c, which i haven't tried to compile, but i think the executable is under 64k. this might give the flavor of the language thus implemented:

    ; ::::::::::::
    ; :: Turtle ::
    ; ::::::::::::

    ; Define "Turtle" class
    (setq Turtle (Class 'new))

    ; Define instance variables
    (Turtle 'ivars '(xpos ypos char))

    ; Answer "isnew" by initing a position and char and displaying.
    (Turtle 'answer 'isnew '() '(
        (setq xpos (setq newx (+ newx 1)))
        (setq ypos 12)
        (setq char "*")
        (self 'display)
        self))

https://www.softwarepreservation.org/projects/LISP/picolisp/... purports to be a lisp interpreter in an 8-kibibyte executable. for cp/m. it looks like it's cp/m-80, since objdump -D -b binary -m i386 -M i8086,intel --adjust-vma=0x100 8kl.com produces gibberish. dz80 from the d52 package produces a reasonable-looking disassembly, but it's 6000 lines long, and i don't have a cp/m or cp/mish emulation environment set up at the moment, so i can't verify that it actually works. all the source code is included

still, it seems like pretty strong evidence that you can do an ergonomic embedded scripting language in 8 kilobytes or so, not 1900 kilobytes