I was about to post similar because in the git repo it also states:

> Pocketlang is a small (~3000 semicolons) and fast functional language written in C

From what I can tell from the comments, pocketlang re-uses and/or re-implements some functionality from the wren language source code:

    $ grep wren src/*.h src/*.c
    src/pk_compiler.c:  /* String interpolation (reference wren-lang)
    src/pk_utils.h:// Source : https://github.com/wren-lang/wren/blob/main/src/vm/wren_utils.h#L119
    src/pk_utils.h:// Copied from wren-lang.
    src/pk_var.h: * wren (https://wren.io/) an awesome language written by Bob Nystrom the
    src/pk_var.h: *     https://github.com/wren-lang/wren/blob/main/src/vm/wren_value.h
    src/pk_var.h:// usage and it has 2 formated characters (just like wren does).