No, no. I mean this:
my @actual_data = (
[ ... ],
[ ... ],
[ ... ],
);
my %index_of = (
foo => 0,
bar => 1,
baz => 2,
);
my @key_for = qw( foo bar baz );
my $lookup_by_key = $actual_data[ $index_of{ 'bar' } ];
my $lookup_by_idx = $actual_data[ 1 ];
my $key_from_idx = $key_for[ 1 ];
When you move things around in @actual_data, you need to the move the keys around in exactly the same fashion in @key_for. You also need to collect all keys whose values changed positions and update them in %index_of accordingly. To just swap two elements, this is trivial:
sub swap_elements_by_idx {
my ( $i, $j ) = @_;
@actual_data[ $i, $j ] = @actual_data[ $j, $i ];
@key_for[ $i, $j ] = @key_for[ $j, $i ];
@index_of{ @key_for[ $i, $j ] } = @index_of{ @key_for[ $j, $i ] };
}
Reformulating this for atomic operations involving more than two elements is trickier, since the order of operations is then significant, but shouldn't be very hard either.
Makeshifts last the longest.
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