IPC::Open3::xclose hotpatch

[Andy Armstrong]

I've just found myself staring at the code in  
TAP::Parser::Iterator::Process that hotpatches IPC::Open3 so that  
STDIN isn't clobbered by xclose. The code looks like this:

         # HOTPATCH {{{
         my $xclose = \&IPC::Open3::xclose;
         local $^W;    # no warnings
         local *IPC::Open3::xclose = sub {
             my $fh = shift;
             no strict 'refs';
             return if ( fileno($fh) == fileno(STDIN) );
             $xclose->($fh);
         };

         # }}}

(starts at T::P::I::P, line 119)

I'm wondering how / whether it works. The patch is localised; surely  
by the time xclose is called the patch will have gone out of scope and  
xclose will have reverted to its normal implementation?

Am I missing something?

-- 
Andy Armstrong, Hexten