perl -e 'package B;
 sub foo {};
 sub bar {};

 package A;
 @A::ISA="B";
 sub bar {};
 sub baz {};
 for (qw(foo bar baz)) {
  print "$_: "
   .(A->can($_) == B->can($_) ? " same" : " overwritten")
   ."\n"}'

##</code><code>##

foo:  same
bar:  overwritten
baz:  overwritten