package C; use lib qw(.); use vars qw(@ISA); use strict; BEGIN { use vars qw(@ISA); if ($^O eq "MSWin32") { #Windows @ISA=qw(B); require qw(B.pm); } else { #Linux @ISA=qw(A); require qw(A.pm); } return 1; } sub AUTOLOAD { my ($func)=@_; print "Function not found $func \n"; print Dumper \@ISA; } 1;