Questions before proceeding to ChangeLog entries & regression tests:

1. Is this something we would like Emacs to recognize out of the box, or
is it too niche?

2. What about the more general forms shown in (info "(coreutils) env
invocation")?

  #!/usr/bin/env -[v]S[OPTION]... [NAME=VALUE]... COMMAND [ARGS]...

3. Assuming we do want to amend that regexp, would it be possible to use
rx here?  OT1H guessing "no" because files.el is pre-reloaded, whereas
rx.el is not; OTOH I see that files.el requires easy-mmode at
compile-time, and that package does not show up in loadup.el, so…
settling for "maybe?"

WDYT?


In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.37, cairo version 1.16.0) of 2023-08-20 built on hirondell
Repository revision: 652e45b70d82e6f615febe00553dbded80557845
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101007
System Description: Debian GNU/Linux 12 (bookworm)

Configured using:
 'configure
 --cache-file=/home/peniblec/.cache/emacs/config,src,emacs,master
 --with-cairo --with-gconf --with-sqlite3 --with-xinput2'

Configured features:
ACL CAIRO DBUS FREETYPE GCONF GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix