I mean this behavior:

#!/usr/bin/perl -l

$y='main';$A::y='A';$C::y='C';

package main;

sub foo { $y }
sub bar { $y }

package A;

*foo = \&main::foo;
*bar = \&main::bar;

package C;

@C::ISA = 'A';

*bar = \&main::bar;

package main;

use B 'svref_2object';

my $x = bless {}, 'C';
for (qw(foo bar)) {
    print "$_ -> ", $x->$_, " from ", svref_2object(UNIVERSAL::can($x,
+ $_))->GV->STASH->NAME;
}
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If you know the name of the intended destination stash at the time of writing the code, your example works fine. It's not always possible to know that, unfortunately.