my %foo = qw( a 1 b 2 );
my %bar = qw( a 1 b 2 );

%foo = qw( c 3 d 4 );
@bar{qw( c d )} = qw( 3 4 );

print(join(' ', %foo), "\n");  # c 3 d 4
print(join(' ', %bar), "\n");  # a 1 b 2 c 3 d 4