> It’s not needed.  All that needed is the name of the executable file
> to wrap.

I don't understand.  How will 'rename-file' get the location of the
executable?  For example:

(wrap-program "wget" [...])

I guess that it will only work if you invoke 'wrap-program' from the
same directory.

> For the case where there are have several variables you want to set.

Could you provide an example?  The following works without '#:rest':

(display (wrap-program "wget" '(("PATH" ":" = ("/nix/.../gawk/bin"))
                                ("CERT_PATH" ":" suffix ("/nix/.../share/certs"
                                                         "/nix/.../foo/certs")))))

#!/bin/bash
export PATH="/nix/.../gawk/bin"
export CERT_PATH="$CERT_PATH${CERT_PATH:+:}:/nix/.../share/certs:/nix/.../foo/certs"
exec ./.wget-real