use strict;
use warnings;

package X::Y::Z::my;                    # sub package

sub xyz {warn "xyz called" }


package Y::Y::Z;

BEGIN {
    *::my:: = *X::Y::Z::my:: ;          # alias sub package to my::
}

# END {                                 # delete alias at file's end
#     delete $::{"my::"};
# }



my::xyz();


BEGIN {                                 # delete alias here for demo
    delete $::{"my::"};
}

package Other;

my::xyz();                              # fails alias already gone




##</code><code>##

C:/Perl_524/bin\perl.exe  d:/exp/local_package.pl 
xyz called at d:/exp/local_package.pl line 6.
Undefined subroutine &my::xyz called at d:/exp/local_package.pl line 30.