#! perl
use strict;
use warnings;
use Data::Dump;
use Hash::MoreUtils qw(safe_reverse);

my  %t = ( a => 1, b => 2, c => 1, d => 2, e => 1, f => 2 );
dd \%t;

my  %dup_rev = safe_reverse \%t;
dd \%dup_rev;