replace the current XS 'bad handshake" wording with more informative text

[nwc10]

On Thu, Sep 09, 2021 at 03:07:46AM -0700, Nicholas Clark wrote:

xs_handshake() makes two different comparisons that on failure are reported
as "got handshake key %p, needed %p", with opaque hexadecimal values.

Personally I'd go further. This message most often appears when modules
built with one version of perl are loaded by a different perl binary. This
is a fairly common occurrence (e.g. if PERL5LIB is set), and the message
is horrible. It's going on about a 'handshake' having the wrong hex key,
and just scares the user without saying anything useful.

Personally I think the error message should:

• remove any mention of 'handshake' (it makes it sound like some sort of
  network error);

• should be a lot more verbose, suggesting (where relevant) that its
  likely a mismatch between perl version/build and module build, and
  displaying (where relevant) the @inc path and relevant PERL env vars.
  So, a bit like how we improved the 'module not found' error:

  Can't locate Foo/Bar.pm in @inc (you may need to install the Foo::Bar
  module) @.*** contains: ....).

• If the hex values have any further useful info, they should be
  symbolically decoded if possible.

--
In my day, we used to edit the inodes by hand. With magnets.

Originally posted by @iabyn in #19111 (comment)