diff --git a/faden.lua b/faden.lua
index 337fbf7..2356352 100644
--- a/faden.lua
+++ b/faden.lua
@@ -2,7 +2,11 @@ local function befehl_ausfuhren(faden)
 	local is = faden.is
 	local imms = faden.imms
 	local vars = faden.vars
-	local befehl, args = unpack(faden.liste[faden.ip])
+	local anw = faden.liste[faden.ip]
+	if not anw then
+		return false, "Invalid instruction pointer"
+	end
+	local befehl, args = unpack(anw)
 	for i = 1,#is do
 		local bfunk = is[i][befehl]
 		if bfunk then
@@ -64,8 +68,9 @@ return function(faden_manip, parsed)
 		log = "",
 		vars = {pi = math.pi},
 		ip = 1,
-		sp = 50,
-		sb = 50,
+		sp = 3500,
+		sb = 3500,
+		strlen_max = 2000,
 		stack = {},
 		is = {pdisc.standard_befehlssatz},
 		suscitate = programm_ausfuhren,
@@ -93,6 +98,12 @@ return function(faden_manip, parsed)
 	if parsed then
 		faden.imms = parsed[1]
 		faden.liste = parsed[2]
+		if not faden.liste[1] then
+			faden.suscitate = function(self)
+				self.log = self.log .. "Nothing to execute.\n"
+				self:exit()
+			end
+		end
 	end
 	faden_manip(faden)
 	return faden
diff --git a/standardbefehlssatz.lua b/standardbefehlssatz.lua
index 7d974d0..b41ea98 100644
--- a/standardbefehlssatz.lua
+++ b/standardbefehlssatz.lua
@@ -1,6 +1,7 @@
 local WNOA = "wrong number of arguments"
 local UAT = "unsupported argument type"
 local SE = "error with cmd-cmd executing: "
+local STRL = "attempt on exceeding maximum string length"
 
 local s
 s = {
@@ -11,7 +12,7 @@ s = {
 		return true, params[2]
 	end,
 
-	add = function(params)
+	add = function(params, faden)
 		if #params ~= 2 then
 			return false, WNOA
 		end
@@ -28,6 +29,9 @@ s = {
 		if t1 == "boolean" then
 			return true, p1 and p2
 		end
+		if #p1 + #p2 > faden.strlen_max then
+			return false, STRL
+		end
 		return true, p1 .. p2
 	end,
 
@@ -40,6 +44,9 @@ s = {
 		local t2 = type(p2)
 		if t1 == "string"
 		and t2 == "number" then
+			if #p1 * p2 > faden.strlen_max then
+				return false, STRL
+			end
 			return true, p1:rep(p2)
 		end
 		if t1 ~= t2 then
@@ -125,6 +132,33 @@ s = {
 		return true
 	end,
 
+	call = function(params, faden)
+		if #params ~= 1 then
+			return false, WNOA
+		end
+		local subsucc,msg = s.push(faden.ip + 1, faden)
+		if not subsucc then
+			return false, SE .. msg
+		end
+		subsucc,msg = s.jmp(params, faden)
+		if not subsucc then
+			return false, SE .. msg
+		end
+		return true
+	end,
+
+	ret = function(_, faden)
+		local subsucc,msg = s.pop({true}, faden)
+		if not subsucc then
+			return false, SE .. msg
+		end
+		subsucc,msg = s.jmp({msg}, faden)
+		if not subsucc then
+			return false, SE .. msg
+		end
+		return true
+	end,
+
 	push = function(params, faden)
 		local pc = #params
 		if pc == 0 then
@@ -192,6 +226,21 @@ s = {
 		return true
 	end,
 
+	sleep = function(params, faden)
+		if #params ~= 1 then
+			return false, WNOA
+		end
+		local p = params[1]
+		if type(p) ~= "number" then
+			return false, UAT
+		end
+		subsucc,msg = s.usleep({p * 1000000}, faden)
+		if not subsucc then
+			return false, SE .. msg
+		end
+		return true
+	end,
+
 	get_us_time = function()
 		return true, minetest.get_us_time()
 	end,
@@ -216,7 +265,7 @@ s = {
 	end,
 }
 
-local so_math_fcts = {"sin", "asin", "cos", "acos", "tan", "atan",
+local so_math_fcts = {"sin", "asin", "cos", "acos", "tan", "atan", "exp", "log",
 	"abs", "sign", "floor", "ceil"}
 for i = 1,#so_math_fcts do
 	i = so_math_fcts[i]
@@ -231,4 +280,21 @@ for i = 1,#so_math_fcts do
 		return true, math[i](p)
 	end
 end
+
+local to_math_fcts = {"pow"}
+for i = 1,#to_math_fcts do
+	i = to_math_fcts[i]
+	s[i] = function(params)
+		if #params ~= 2 then
+			return false, WNOA
+		end
+		local p1,p2 = unpack(params)
+		if type(p1) ~= "number"
+		or type(p2) ~= "number" then
+			return false, UAT
+		end
+		return true, math[i](p1, p2)
+	end
+end
+
 return s