package Class::HideMethods;

use strict;
use warnings;
use Attribute::Handlers;

sub import
{
   my ($self,$ref) = @_;
   my $package = caller();
   $prefixes{ $package } = $ref;
}

sub gen_prefix
{
  my $invalid_chars = "\0\r\n\f\b";

  my $prefix;

  for (1..5){
    my $chars_pos = int (rand(length($invalid_chars)));
    $prefix .= substr ($invalid_chars, $char_pos, 1);
  }
  return $prefix;
}

package UNIVERSAL;

sub Private :ATTR
{
  my ($package, $symbol, $referent, $attr, $data, $phase) = @_;

  my $name = *{ $symbol }{NAME};
  my $newname = Class::HideMethods::gen_prefix ($package) . $name;
  my @refs = map { *$symbol{$_}} qw (HASH SCALAR ARRAY GLOB);
  *$symbol = do {local *symbol};

  no strict 'refs';
  *{ $package . '::' . $newname } = $referent;
  *{ $package . '::' . $name    } = $_ for @refs;
  $prefixes{ $package }{$name}    = $newname;
}

1;
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To use this module:

package SecretClass;

my %methods;
use Class::HideMethods \%methods;

sub new            { bless {}, shift  }
sub hello :Private { return 'hello'   }
sub goodbye        { return 'goodbye' }

sub public_hello
{
  my $self = shift;
  my $hello = $methods{hello}
  $self -> $hello();
}
1;
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To prove that it works:

use Test::More tests => 6;
my $sc = SecretClass->new();
isa_ok ($sc, 'SecretClass' );

ok (! $sc->can ('hello'), 'hello() should be hidden' );
ok ($sc->can('public_hello'), 'public_hello() should be available');
is ($sc->public_hello(),'hello', '... and should be able to call hello
+()' );
ok ($sc->can('goodbye'), 'goodbye() should be available');
is ($sc->goodbye(), 'goodbye', '... and should be callable');
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