#!/usr/bin/perl
use Data::Dumper;

%hash1 = (a=>1,b=>2,c=>3); 
%hash2 = (1=>'A',2=>'B'); 

@hash3{keys %hash1}= @hash2{values %hash1};
#defined $hash3{$_} or delete $hash3{$_} for keys %hash3;

print Dumper \%hash3; 

__END__
$VAR1 = {
          'c' => undef,
          'a' => 'A',
          'b' => 'B'
        };