Add week 9 challenge #2 for Perl 6

challenge-009/daniel-mita/perl6/ch-2.p6

@@ -0,0 +1,75 @@
+#!/usr/bin/env perl6
+use v6;
+
+my %*SUB-MAIN-OPTS = :named-anywhere;
+
+subset ScoreList of List where { .elems > 1 && $_ %% 2 && .[1,3…*].all ~~ Numeric };
+
+#| "1224" Ranking.
+multi MAIN (
+  Bool :standard(:$s), #= Use Standard Ranking. Default if no ranking is provided.
+  *@scores where * ~~ ScoreList,
+) {
+  my %table = create-table(@scores);
+  for %table.keys.sort(&infix:«<=>»).reverse -> $score {
+    state $place = 1;
+    "$place: $_".say for %table{$score}.values.sort;
+    $place += %table{$score}.elems;
+  }
+}
+
+#| "1334" Ranking.
+multi MAIN (
+  Bool :modified(:$m)! where *.so, #= Use Modified Ranking.
+  *@scores where * ~~ ScoreList,
+) {
+  my %table = create-table(@scores);
+  for %table.keys.sort(&infix:«<=>»).reverse -> $score {
+    state $place;
+    $place += %table{$score}.elems;
+    "$place: $_".say for %table{$score}.values.sort;
+  }
+}
+
+#| "1223" Ranking.
+multi MAIN (
+  Bool :dense(:$d)! where *.so,  #= Use Dense Ranking.
+  *@scores where * ~~ ScoreList, #= An even list of alternating names and scores. Higher score ranks higher.
+) {
+  my %table = create-table(@scores);
+  for %table.keys.sort(&infix:«<=>»).reverse -> $score {
+    state $place = 1;
+    "$place: $_".say for %table{$score}.values.sort;
+    $place++;
+  }
+}
+
+multi GENERATE-USAGE (
+  &main,
+  Bool :standard(:$s),
+  Bool :modified(:$m),
+  Bool :dense(:$d) where { none(.one, .none) given @($s, $m, $d) },
+) {
+  "Error: Cannot use more than one rank type.\n\n" ~ GENERATE-USAGE(&main);
+}
+
+multi GENERATE-USAGE(&main, |) {
+  $*USAGE ~ q:to/DOC/;
+
+
+    Example:
+      perl6 ch-2.p6 --dense foo 3 bar 8 baz 1 fizz 3 buzz 6
+
+      1: bar
+      2: buzz
+      3: fizz
+      3: foo
+      4: baz
+    DOC
+}
+
+sub create-table (Array $_) {
+  my %table;
+  %table{.[1]}.push(.[0]) for .rotor(2);
+  return %table;
+}