examples: lang: Test that each of the mcl examples compiles

We let these rot, so fixup the issues and test them!

examples/lang/polymorphic-lambda.mcl

@@ -1,19 +1,19 @@
 import "fmt"
 
-$add = func($x) {
+func add($x) { # if this was a lambda, type unification would fail! (not allowed)
 	$x + $x
 }
 
 $num = 2
-$out1 = $add($num) # 4
+$out1 = add($num) # 4
 
-print fmt.printf("%d + %d is %d", $num, $num, $out1) { # simple math
+print [fmt.printf("%d + %d is %d", $num, $num, $out1),] { # simple math
 	Meta:autogroup => false,
 }
 
 $val = "hello"
-$out2 = $add($val) # hellohello
+$out2 = add($val) # hellohello
 
-print fmt.printf("%s + %s is %s", $val, $val, $out2) { # simple concat
+print [fmt.printf("%s + %s is %s", $val, $val, $out2),] { # simple concat
 	Meta:autogroup => false,
 }