Revert use_ok() change to allow lexical effects?

In a series of patches, Father Chrysostomos and I enhanced use_ok() so that it
can apply lexical effects to more closely emulate the real `use`.  For example,

    use_ok('strict');

Previously this would just load strict and call import, but strictures would
not actually be applied to your scope.  Now strictures *will* be applied
making it work more like a regular use.

Testing has shown it's caused just a handful of compatibility problems, and it
hasn't gone out in a stable release yet.  Because the new use_ok() is so much
more complex than before I'm having second thoughts about whether it's worth
it and would like opinions.

There are two questions:

1. Should the lexical effect patches to use_ok() be rolled back?
2. Should use_ok() be discouraged in the documentation?

The new use_ok(), while it works remarkably well, is significantly more
complex than previously and it touches magical variables $^H and %^H.  There
is a danger of invoking bugs by touching those variables.

It continues to have compatibility issues, for example...

    BEGIN {  use_ok 'Some::Module' }

this will apply lexical effect while...

    BEGIN { use strict }

will not but

    BEGIN { require strict; strict->import }

will.  Confusing.

use_ok() has low utility to begin with.  If you want exports and lexical
effects to be properly applied you have to wrap it in a BEGIN block.  And as
has been pointed out before, if use_ok() fails you probably want the program
to halt.  So the full invocation should be...

    BEGIN {
        use_ok("Some::Module") or die;
    }

At which point you might as well write...

    use Some::Module;

And if you really want the load to be a passing test, you can add...

    pass("Loaded Some::Module");

If all you want to do is check that a module can compile, there is the much
simpler require_ok().

Apologies to Father Chrysostomos if his work is reverted, it has been top
notch.  If it is reverted, it may find life in another module where a complete
emulation of use is desired as a user function or method.


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