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 ];