Brilliant pointers! Thanks to metacpan and this amazing fellow ( https://cpan.metacpan.org/authors/id/J/JH/JHI/ ) who's kept antique source alive, I was able to build a working test version with no dramas (perl5.7.3 being the documented last time this worked) 
2023/11/12 12:17.12   1,065,256   microperl

[download]
That's on my 64bit intel; a 32bit build for xtensa would presumably be even smaller... which leaves at least 600kb space to implement the OS-replacement stuff if I wanted to ship something even smaller than micropython :-)

I apparently only need to implement these: 

- <stddef.h>, <stdlib.h>
- rename()
- opendir(), readdir(), closedir() (via dirent.h)
- memchr(), memcmp(), memcpy(), memset() (via string.h)
- (a safe) putenv() (via stdlib.h)
- strtoul() (via stdlib.h)

$ ./microperl -v

This is perl, v5.7.3 built for unknown

Copyright 1987-2002, Larry Wall

[download]

In reply to Re: Building a MicroPerl distro for ESP32 and similar MCUs ? by cnd
in thread Building a MicroPerl distro for ESP32 and similar MCUs ? by cnd

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.