[perl #91614] Suggestion for improving documentation of $!

[perl #91614] Suggestion for improving documentation of $!

While trying to understand a bug report at

http://www.perlmonks.org/?node_id=906466

I realized that the documentation for $! was not crystal clear.  For example

    If used numerically, yields the current value of the
    C C<errno> variable, or in other words,
    if a system or library call fails, it sets this variable.

That's not "in other words", these are totally different
concepts.  And it isn't clear whether this variable refers to
errno or $! (I assumed the latter, and was wrong, as Devel::Peek
demonstrated).  And $! cannot be undef, as asserted (later),
because errno always contains a value, however irrelevant.