use Data::Dumper;
my %hash = ( foo => 1, bar => 2 );
warn Dumper(\%hash);
{
    local @hash{qw/bar moose/} = qw/happy joy/;
    warn Dumper(\%hash);
}
warn Dumper(\%hash);
__END__
$VAR1 = {
          'bar' => 2,
          'foo' => 1
        };
$VAR1 = {
          'bar' => 'happy',
          'moose' => 'joy',
          'foo' => 1
        };
$VAR1 = {
          'bar' => 2,
          'foo' => 1
        };