It's really just a nit, but you're leaking an alias to @Foo::Bar::ISA. I also use BEGIN {} instead of {} inlined modules. I'd write your program as: 

#!/usr/bin/perl
use strict;
use warnings;

BEGIN {
   package Foo;

   sub method {
       routine();
   }

   sub routine {
       return __PACKAGE__;
   }
}

BEGIN {
   package Foo::Bar;
   our @ISA = qw( Foo );

   sub routine {
       return __PACKAGE__;
   }

   sub method {
       no warnings 'redefine';
 
       # Temporarily override routine() in the parent class.
       local *Foo::routine = \&routine;
    
       # Delegate to parent method.
       my $self = shift;
       $self->SUPER::method(@_);
   }
}

print "Foo:      ", Foo->method, "\n";
print "Foo::Bar: ", Foo::Bar->method, "\n";
print "Foo:      ", Foo->method, "\n";

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In reply to Re^4: Overridding subroutines called in private subroutines by ikegami
in thread Overridding subroutines called in private subroutines by skazat

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