diff --git a/nselib/cvs.lua b/nselib/cvs.lua
index 6ca28c7d6..ca64aa11d 100644
--- a/nselib/cvs.lua
+++ b/nselib/cvs.lua
@@ -86,11 +86,8 @@ Util = {
       182,128,158,208,162,132,167,209,149,241,153,251,237,236,171,195,
       243,233,253,240,194,250,191,155,142,137,245,235,163,242,178,152 };
 
-    local result = ""
-    for i = 1, #password do
-      result = result .. string.char(shifts[password:byte(i)+1])
-    end
-    return 'A' .. result
+    return 'A' .. string.gsub(password, ".",
+      function(c) return string.char(shifts[c:byte()+1]) end)
   end
 
 }
diff --git a/nselib/drda.lua b/nselib/drda.lua
index 257577059..f96d47cfd 100644
--- a/nselib/drda.lua
+++ b/nselib/drda.lua
@@ -751,13 +751,10 @@ StringUtil =
   -- @param ascii string containing the ASCII value
   -- @return string containing the EBCDIC value
   toEBCDIC = function( ascii )
-    local ret = ""
-
-    for i=1, #ascii do
-      local val = ascii.byte(ascii,i) + 1
-      ret = ret .. a2e_tbl:sub(val, val)
-    end
-    return ret
+    return string.gsub(ascii, ".", function(a)
+        local val = a:byte() + 1
+        return a2e_tbl:sub(val, val)
+      end)
   end,
 
   --- Converts an EBCDIC string to ASCII
@@ -765,13 +762,10 @@ StringUtil =
   -- @param ebcdic string containing EBCDIC value
   -- @return string containing ASCII value
   toASCII = function( ebcdic )
-    local ret = ""
-
-    for i=1, #ebcdic do
-      local val = ebcdic.byte(ebcdic,i) + 1
-      ret = ret .. e2a_tbl:sub(val, val)
-    end
-    return ret
+    return string.gsub(ebcdic, ".", function(e)
+        local val = e:byte() + 1
+        return e2a_tbl:sub(val, val)
+      end)
   end,
 
   --- Pads a string with a character
diff --git a/nselib/mssql.lua b/nselib/mssql.lua
index 46a2b36d4..7f9aedb8d 100644
--- a/nselib/mssql.lua
+++ b/nselib/mssql.lua
@@ -3064,15 +3064,13 @@ Auth = {
   -- @return string containing the encrypted password
   TDS7CryptPass = function(password)
     local xormask = 0x5a5a
-    local result = ""
 
-    for i=1, password:len() do
-      local c = bit.bxor( string.byte( password:sub( i, i ) ), xormask )
+    return password:gsub(".", function(i)
+      local c = bit.bxor( string.byte( i ), xormask )
       local m1= bit.band( bit.rshift( c, 4 ), 0x0F0F )
       local m2= bit.band( bit.lshift( c, 4 ), 0xF0F0 )
-      result = result .. bin.pack("S", bit.bor( m1, m2 ) )
-    end
-    return result
+      return bin.pack("S", bit.bor( m1, m2 ) )
+    end)
   end,
 
   LmResponse = function( password, nonce )
diff --git a/nselib/netbios.lua b/nselib/netbios.lua
index 01e34de30..b028d9929 100644
--- a/nselib/netbios.lua
+++ b/nselib/netbios.lua
@@ -101,13 +101,12 @@ function name_decode(encoded_name)
 
   stdnse.debug3("Decoding name '%s'", encoded_name)
 
-  for i = 2, len + 1, 2 do
-    local ch = 0
-    ch = bit.bor(ch, bit.lshift(string.byte(encoded_name, i)     - 0x41, 4))
-    ch = bit.bor(ch, bit.lshift(string.byte(encoded_name, i + 1) - 0x41, 0))
-
-    name = name .. string.char(ch)
-  end
+  name = name:gsub("(.)(.)", function (a, b)
+      local ch = 0
+      ch = bit.bor(ch, bit.lshift(string.byte(a) - 0x41, 4))
+      ch = bit.bor(ch, bit.lshift(string.byte(b) - 0x41, 0))
+      return string.char(ch)
+    end)
 
   -- Decode the scope
   local pos = 34
diff --git a/nselib/rmi.lua b/nselib/rmi.lua
index 1cbac885e..6c09a4a04 100644
--- a/nselib/rmi.lua
+++ b/nselib/rmi.lua
@@ -1156,16 +1156,9 @@ end
 -- returns the string with all non-printable chars
 -- coded as hex
 function makeStringReadable(data)
-  local r = ""
-  for i=1,#data,1 do
-    local x = data:byte(i)
-    if x > 31 and x <127 then
-      r = r .. data:sub(i,i)
-    else
-      r = r .. ("\\x%x"):format(x)
-    end
-  end
-  return r
+  return data:gsub("[\x00-\x1f\x7f-\xff]", function (x)
+      return ("\\x%02x"):format(x:byte())
+    end)
 end
 
 function readNonProxyDesc(dis)