bugfix for backtracking over RET insns, and a truly evil testcase

c/testdata

@@ -138,6 +138,11 @@ def f: . + 1; def g: def g: . + 100; $$f | $$g | $$f; ($$f | $$g), $$g
 106.0
 105.0
 
-[[100,200][] as $x | def f: . + $x; $$f | $$f | $$f]
-1
-[301.0, 601.0]
+def f: (1000,2000); $$f
+123412345
+1000
+2000
+
+[[20,10][1,0] as $x | def f: (100,200) as $y | def g: [$x + $y, .]; . + $x | $$g; $$f[0] | [$$f][0][1] | $$f]
+"woo, testing!"
+[[110.0, 130.0], [210.0, 130.0], [110.0, 230.0], [210.0, 230.0], [120.0, 160.0], [220.0, 160.0], [120.0, 260.0], [220.0, 260.0]]