#!/usr/bin/perl --
package NameSpace;

use constant 1  +{qw{ RO 1 SHAM 2 BO 3 }};

BEGIN { print "before clean ", join ' ', keys \%NameSpace::, "\n"; }

use namespace::clean;
use namespace::clean qw[ RO SHAM BO ];

BEGIN { print "after clean ", join ' ', keys \%NameSpace::, "\n"; }

printf  "SHAM?? %s  \n", SHAM();
1;
__END__
$ perl -e " do 'yo'; print NameSpace::SHAM() "
before clean BEGIN RO BO SHAM
after clean BEGIN __NAMESPACE_CLEAN_STORAGE RO BO SHAM
SHAM?? 2
2