Challenge 2 done.

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+#!env raku
+#
+#Wave Array
+#
+# Any array N of non-unique, unsorted integers can be arranged
+# into a wave-like array such that n1 ≥ n2 ≤ n3 ≥ n4 ≤ n5 and so on.
+#
+# For example, given the array [1, 2, 3, 4],
+# possible wave arrays include [2, 1, 4, 3] or [4, 1, 3, 2],
+# since 2 ≥ 1 ≤ 4 ≥ 3 and 4 ≥ 1 ≤ 3 ≥ 2. This is not a complete list.
+#
+# Write a script to print all possible wave arrays
+# for an integer array N of arbitrary length.
+#  Notes:
+#
+# When considering N of any length,
+# note that the first element is always greater
+# than or equal to the second, and then the ≤, ≥, ≤, …
+# sequence alternates until the end of the array.
+
+
+# Test if a single sequence is ok.
+# The third argument checks if the test has to be done as >= or <=.
+sub is-ok( Int:D $a, Int:D $b, Bool:D $greater ) {
+    return $a >= $b if ( $greater );
+    return $a <= $b if ( ! $greater );
+}
+
+
+sub MAIN( Int:D $number where { $number.chars > 1 } ){
+    my @array = $number.comb;
+
+    say "Waving { @array } of { @array.elems } elements ";
+    for @array.permutations -> @current {
+        my $ok = False;
+        my $test = True; # true = greater
+        my @result;
+        for 0 ..^ @current.elems - 1 -> $index {
+            $ok   = is-ok @current[ $index ].Int, @current[ $index + 1 ].Int, $test;
+            $test = ! $test;
+            @result.push( @current[ $index ].Str ~ ( $test ?? ' ≥ ' !! ' ≤ ' ) ); 
+            last if ! $ok;
+        }
+
+        if $ok {
+            @result.push( @current[ *-1 ].Str ~ ( $test ?? ' ≥ ' !! ' ≤ ' ) );
+            say @result;
+        }
+      
+        say "Found wave { @current }" if $ok;
+    }
+}