March 2014 update

Task/Mutual-recursion/Perl/mutual-recursion.pl

@@ -1,13 +1,7 @@
-use strict;
-use warnings;
+sub F { my $n = shift; $n ? $n - M(F($n-1)) : 1 }
+sub M { my $n = shift; $n ? $n - F(M($n-1)) : 0 }
 
-# For mutually recursive functions,
-# predeclaring is probably a good idea.
-sub M; sub F;
-
-sub F { my $n = shift; $n ? $n - M F $n-1 : 1 }
-sub M { my $n = shift; $n ? $n - F M $n-1 : 0 }
-
-for my $f (\&F, \&M) {
-    print join(' ', map $f->($_), 0 .. 19), "\n";
+# Usage:
+foreach my $sequence (\&F, \&M) {
+    print join(' ', map $sequence->($_), 0 .. 19), "\n";
 }