Today I wanted to generate a list from another list. Typically I would use map for this, but I wanted to iterate over two elements at a time, instead of one at a time. (A lot of people said to use natatime from List::MoreUtils, over and over. They didn’t read my question very carefully, especially since I specifically said I wanted natatime but with map.)

Anyway, mst pointed out Perl6::Gather, which works perfectly for this situation! Ah the beauty of Perl 6 in Perl 5. Here are the codez:

1
2
3
4
5
6
7
8
9
my @list = (
  foo => [qw{bar baz biff}],
);

my @new_list = gather {
  while (my ($foo, $bar) = splice(@list, 2, 0) ) {
     take map { "$foo/$_" } @list;
  }
};

So basically what that does is create an implicit accumulator and every time you call take it adds the arguments to take to the accumulator. In Perl 6 map can iterate over multiple items at once, so this would be silly in that context, but in Perl 5 it’s quite helpful!