search_isa() is simply @ISA, because can searches the whole inheritance tree of the supplied class.

use strict;
use warnings;

package AA;

sub dostuff { print(scalar(caller()), $/); }


package BB;


package CC;

BEGIN { our @ISA = 'AA'; }


package DD;

use vars qw(@ISA);
BEGIN { @ISA = qw(BB CC); }

sub dostuff {
   foreach my $super (@ISA) {
     #if (my $method = $super->can('dostuff')) {
     #  -or-
      if (my $method = UNIVERSAL::can($super, 'dostuff')) {
         #print($super,  $/);
         #print($method, $/);
         goto $method;
      }
   }
}


package main;

#print(\&AA::dostuff, $/);

bless({},'DD')->dostuff();  # Prints "main"
[download]