package Foo;

sub _F_method1 { print "Foo::_method\n"; }
sub method2 { my $self = shift; $self->_F_method1; }


package Foo::Bar;

@ISA = qw( Foo );

sub _F_B_method1 { print "Foo::Bar::_method\n"; }

package main;

my $foobar = Foo::Bar->new;
$foobar->method2;