Add all the A tasks

Task/Anonymous-recursion/Tcl/anonymous-recursion-1.tcl

@@ -0,0 +1,10 @@
+proc fib n {
+    # sanity checks
+    if {[incr n 0] < 0} {error "argument may not be negative"}
+    apply {x {
+	if {$x < 2} {return $x}
+	# Extract the lambda term from the stack introspector for brevity
+	set f [lindex [info level 0] 1]
+	expr {[apply $f [incr x -1]] + [apply $f [incr x -1]]}
+    }} $n
+}

Task/Anonymous-recursion/Tcl/anonymous-recursion-2.tcl

@@ -0,0 +1 @@
+puts [fib 12]

Task/Anonymous-recursion/Tcl/anonymous-recursion-3.tcl

@@ -0,0 +1,9 @@
+proc fib n {
+    if {[incr n 0] < 0} {error "argument may not be negative"}
+    apply {x {expr {
+        $x < 2
+          ? $x
+          : [apply [lindex [info level 0] 1] [incr x -1]]
+            + [apply [lindex [info level 0] 1] [incr x -1]]
+    }}} $n
+}

Task/Anonymous-recursion/Tcl/anonymous-recursion-4.tcl

@@ -0,0 +1,8 @@
+# Pick the lambda term out of the introspected caller's stack frame
+proc tcl::mathfunc::recurse args {apply [lindex [info level -1] 1] {*}$args}
+proc fib n {
+    if {[incr n 0] < 0} {error "argument may not be negative"}
+    apply {x {expr {
+        $x < 2 ? $x : recurse([incr x -1]) + recurse([incr x -1])
+    }}} $n
+}