diff --git a/anagrams.tlv b/anagrams.tlv
index 14f3d21..a314eb8 100644
--- a/anagrams.tlv
+++ b/anagrams.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,11 +32,11 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
     >    return table.concat(t)
     >  end
@@ -186,7 +186,7 @@
   count_letters:
     >function count_letters(s)
     >  local result = {}
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    local c = s[i]
     >    if result[c] == nil then
     >      result[c] = 1
@@ -309,8 +309,8 @@
     >Mon Feb 21 18:06:20 2022
   take_out:
     >function take_out(s, i)
-    >  if i < 1 then return string.sub(s, 1) end
-    >  return string.sub(s, 1, i-1) .. string.sub(s, i+1)
+    >  if i < 1 then return s:sub(1) end
+    >  return s:sub(1, i-1) .. s:sub(i+1)
     >end
     >
     >function test_take_out()
@@ -342,7 +342,7 @@
     >Sat Mar  5 15:24:00 2022
   count_anagrams:
     >function count_anagrams(s)
-    >  local result = factorial(string.len(s))
+    >  local result = factorial(s:len())
     >  local letter_counts = count_letters(s)
     >  for k, v in pairs(letter_counts) do
     >    result = result / factorial(v)
diff --git a/commander.tlv b/commander.tlv
index 6b80304..e6854fc 100644
--- a/commander.tlv
+++ b/commander.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,13 +32,13 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
-    >    return table.concat(t)
+    >    return t:concat()
     >  end
     >end
     >
diff --git a/gemini.tlv b/gemini.tlv
index 3a163f0..5600b3d 100644
--- a/gemini.tlv
+++ b/gemini.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,11 +32,11 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
     >    return table.concat(t)
     >  end
@@ -158,14 +158,14 @@
   render_line:
     >function render_line(window, y, line)
     >  window:mvaddstr(y, 0, '')
-    >  for i=1,string.len(line) do
+    >  for i=1,line:len() do
     >    window:addstr(line[i])
     >  end
     >end
 - __teliva_timestamp: original
   render_link:
     >function render_link(window, y, line)
-    >  local rendered_line = string.gsub(line, '=>%s*%S*%s*', '')
+    >  local rendered_line = line:gsub('=>%s*%S*%s*', '')
     >  if trim(rendered_line) == '' then
     >    rendered_line = line
     >  end
@@ -189,7 +189,7 @@
     >  y = y+2
     >--?   dbg(window, state.highlight_index)
     >  for i, line in pairs(state.lines) do
-    >    if not state.source and string.find(line, '=> ') == 1 then
+    >    if not state.source and line:find('=> ') == 1 then
     >      if state.highlight_index == 0 or i == state.highlight_index then
     >        -- highlighted link
     >        state.highlight_index = i  -- TODO: ugly state update while rendering, just for first render after gemini_get
@@ -276,7 +276,7 @@
 - __teliva_timestamp: original
   is_link:
     >function is_link(line)
-    >  return string.find(line, '=>%s*%S*%s*') == 1
+    >  return line:find('=>%s*%S*%s*') == 1
     >end
 - __teliva_timestamp: original
   next_link:
@@ -384,11 +384,11 @@
     >    local s, status = tcp:receive()
     >    if s == nil then break end
     >    if s == '' then break end
-    >    local header, value = string.match(s, '(.-): (.*)')
+    >    local header, value = s:match('(.-): (.*)')
     >    if header == nil then
     >      print(s)
     >    else
-    >      headers[string.lower(header)] = value
+    >      headers[header:lower()] = value
     >      print(header, value)
     >    end
     >  end
@@ -398,7 +398,7 @@
     >    local s, status = tcp:receive(bytes_remaining)
     >    if s == nil then break end
     >    body = body .. s
-    >    bytes_remaining = bytes_remaining - string.len(s)
+    >    bytes_remaining = bytes_remaining - s:len()
     >    if bytes_remaining <= 0 then break end
     >  end
     >  return body
@@ -436,7 +436,7 @@
     >      if line == nil then break end
     >      table.insert(state.lines, line)
     >    end
-    >  elseif string.sub(type, 1, 5) == 'text/' then
+    >  elseif type:sub(1, 5) == 'text/' then
     >    while true do
     >      local line, err = conn:receive()
     >      if line == nil then break end
@@ -450,7 +450,7 @@
     >-- https://tildegit.org/solderpunk/gemini-demo-2
     >-- returns an array of lines, containing either the body or just an error
     >function gemini_get(url)
-    >  if string.find(url, "://") == nil then
+    >  if url:find("://") == nil then
     >    url = "gemini://" .. url
     >  end
     >  local parsed_url = socket.url.parse(url)
@@ -480,7 +480,7 @@
     >    table.insert(state.lines, err)
     >    return
     >  end
-    >  local status, meta = string.match(line, "(%S+) (%S+)")
+    >  local status, meta = line:match("(%S+) (%S+)")
     >  if status[1] == '2' then
     >    parse_gemini_body(conn, meta)
     >    state.url = url
diff --git a/life.tlv b/life.tlv
index 22293ea..eb9662f 100644
--- a/life.tlv
+++ b/life.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,11 +32,11 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
     >    return table.concat(t)
     >  end
@@ -202,7 +202,7 @@
   count_letters:
     >function count_letters(s)
     >  local result = {}
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    local c = s[i]
     >    if result[c] == nil then
     >      result[c] = 1
@@ -255,7 +255,7 @@
     >    end
     >  end
     >  h.addstr = function(self, s)
-    >    for i=1,string.len(s) do
+    >    for i=1,s:len() do
     >      self:addch(s[i])
     >    end
     >  end
@@ -275,7 +275,7 @@
   kbd:
     >function kbd(keys)
     >  local result = {}
-    >  for i=1,string.len(keys) do
+    >  for i=1,keys:len() do
     >    table.insert(result, keys[i])
     >  end
     >  return result
@@ -298,7 +298,7 @@
   check_screen:
     >function check_screen(window, contents, message)
     >  local x, y = 1, 1
-    >  for i=1,string.len(contents) do
+    >  for i=1,contents:len() do
     >    check_eq(contents[i], window.scr[y][x], message..'/'..y..','..x)
     >    x = x+1
     >    if x > window.scr.w then
@@ -438,7 +438,7 @@
 - __teliva_timestamp: original
   state:
     >function state(line, col)
-    >  if line < 1 or line > table.getn(grid) or col < 1 or col > table.getn(grid[1]) then
+    >  if line < 1 or line > #grid or col < 1 or col > #grid[1] then
     >    return 0
     >  end
     >  return grid[line][col]
@@ -454,9 +454,9 @@
   step:
     >function step()
     >  local new_grid = {}
-    >  for line=1,table.getn(grid) do
+    >  for line=1,#grid do
     >    new_grid[line] = {}
-    >    for col=1,table.getn(grid[1]) do
+    >    for col=1,#grid[1] do
     >      local n = num_live_neighbors(line, col)
     >      if n == 3 then
     >        new_grid[line][col] = 1
diff --git a/lisp.tlv b/lisp.tlv
index 92d23f8..1165cc6 100644
--- a/lisp.tlv
+++ b/lisp.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,11 +32,11 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
     >    return table.concat(t)
     >  end
diff --git a/src/file.lua b/src/file.lua
index bbf9445..cd71f50 100644
--- a/src/file.lua
+++ b/src/file.lua
@@ -56,9 +56,9 @@ function character_splitting_task(chanin, chanout)
   while true do
     local line = chanin:recv()
     if line == nil then break end
-    local linesz = string.len(line)
+    local linesz = line:len()
     for i=1,linesz do
-      chanout:send(string.sub(line, i, i))
+      chanout:send(line:sub(i, i))
     end
   end
   chanout:send(nil)  -- end of file
diff --git a/template.tlv b/template.tlv
index aa78955..ba92fbf 100644
--- a/template.tlv
+++ b/template.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,11 +32,11 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
     >    return table.concat(t)
     >  end
@@ -201,7 +201,7 @@
   count_letters:
     >function count_letters(s)
     >  local result = {}
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    local c = s[i]
     >    if result[c] == nil then
     >      result[c] = 1
@@ -257,7 +257,7 @@
     >    end
     >  end
     >  h.addstr = function(self, s)
-    >    for i=1,string.len(s) do
+    >    for i=1,s:len() do
     >      self:addch(s[i])
     >    end
     >  end
@@ -277,7 +277,7 @@
   kbd:
     >function kbd(keys)
     >  local result = {}
-    >  for i=1,string.len(keys) do
+    >  for i=1,keys:len() do
     >    table.insert(result, keys[i])
     >  end
     >  return result
@@ -299,7 +299,7 @@
   check_screen:
     >function check_screen(window, contents, message)
     >  local x, y = 1, 1
-    >  for i=1,string.len(contents) do
+    >  for i=1,contents:len() do
     >    check_eq(contents[i], window.scr[y][x], message..'/'..y..','..x)
     >    x = x+1
     >    if x > window.scr.w then
diff --git a/toot-toot.tlv b/toot-toot.tlv
index 66b0d9e..3b88688 100644
--- a/toot-toot.tlv
+++ b/toot-toot.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,11 +32,11 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
     >    return table.concat(t)
     >  end
@@ -235,7 +235,7 @@
     >    pos = render_text(window, toot, pos, cursor)
     >    print('')
     >    window:attron(curses.A_BOLD)
-    >    window:addstr(string.len(toot))
+    >    window:addstr(toot:len())
     >    window:attroff(curses.A_BOLD)
     >  end
     >  window:refresh()
@@ -244,7 +244,7 @@
   render_delimiter:
     >function render_delimiter(window, s, pos, cursor)
     >  local newpos = pos
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    if newpos == cursor and i ~= 1 then
     >      if s[i] == '\n' then
     >        -- newline at cursor = render extra space in reverse video before jumping to new line
@@ -290,7 +290,7 @@
     >function render_text(window, s, pos, cursor)
     >  local newpos = pos
     >--?   dbg(window, '--')
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >--?     dbg(window, tostring(newpos)..' '..tostring(string.byte(s[i])))
     >    if newpos == cursor then
     >--?       dbg(window, 'cursor: '..tostring(cursor))
diff --git a/zet.tlv b/zet.tlv
index 0977572..ce10cff 100644
--- a/zet.tlv
+++ b/zet.tlv
@@ -23,7 +23,7 @@
     >-- index characters using []
     >getmetatable('').__index = function(str,i)
     >  if type(i) == 'number' then
-    >    return string.sub(str,i,i)
+    >    return str:sub(i,i)
     >  else
     >    return string[i]
     >  end
@@ -32,11 +32,11 @@
     >-- ranges using (), selected bytes using {}
     >getmetatable('').__call = function(str,i,j)
     >  if type(i)~='table' then
-    >    return string.sub(str,i,j)
+    >    return str:sub(i,j)
     >  else
     >    local t={}
     >    for k,v in ipairs(i) do
-    >      t[k]=string.sub(str,v,v)
+    >      t[k]=str:sub(v,v)
     >    end
     >    return table.concat(t)
     >  end
@@ -201,7 +201,7 @@
   count_letters:
     >function count_letters(s)
     >  local result = {}
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    local c = s[i]
     >    if result[c] == nil then
     >      result[c] = 1
@@ -259,7 +259,7 @@
     >    end
     >  end
     >  h.addstr = function(self, s)
-    >    for i=1,string.len(s) do
+    >    for i=1,s:len() do
     >      self:addch(s[i])
     >    end
     >  end
@@ -279,7 +279,7 @@
   kbd:
     >function kbd(keys)
     >  local result = {}
-    >  for i=1,string.len(keys) do
+    >  for i=1,keys:len() do
     >    table.insert(result, keys[i])
     >  end
     >  return result
@@ -301,7 +301,7 @@
   check_screen:
     >function check_screen(window, contents, message)
     >  local x, y = 1, 1
-    >  for i=1,string.len(contents) do
+    >  for i=1,contents:len() do
     >    check_eq(contents[i], window.scr[y][x], message..'/'..y..','..x)
     >    x = x+1
     >    if x > window.scr.w then
@@ -595,7 +595,7 @@
     >  end
     >  local y, x = top, left + 1  -- left padding; TODO: indent
     >  window:mvaddstr(y, x, '')
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    -- render character
     >    if i == cursor then
     >      if s[i] == '\n' then
@@ -635,7 +635,7 @@
     >      end
     >    end
     >  end
-    >  if cursor > string.len(s) then
+    >  if cursor > s:len() then
     >    window:attron(curses.A_REVERSE)
     >    window:addch(' ')
     >    window:attroff(curses.A_REVERSE)
@@ -676,7 +676,7 @@
 - __teliva_timestamp: original
   cursor_down:
     >function cursor_down(s, old_idx, width)
-    >  local max = string.len(s)
+    >  local max = s:len()
     >  local i = 1
     >  -- compute oldcol, the screen column of old_idx
     >  local oldcol = 0
@@ -767,7 +767,7 @@
     >initial commit: show/edit zettels
   cursor_up:
     >function cursor_up(s, old_idx, width)
-    >  local max = string.len(s)
+    >  local max = s:len()
     >  local i = 1
     >  -- compute oldcol, the screen column of old_idx
     >  local oldcol = 0
@@ -969,7 +969,7 @@
     >  end
     >  local y, x = top, left + 1  -- left padding; TODO: indent
     >  window:mvaddstr(y, x, '')
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    if i == cursor then
     >      cursor_y = y
     >      cursor_x = x
@@ -1010,7 +1010,7 @@
     >  local bottom = top + view_settings.height
     >  local left = (render_state.curr_w - 1) * (view_settings.width + view_settings.hmargin)
     >  local right = left + view_settings.width
-    >  local cursor = string.len(zettels[current_zettel_id].data)+1
+    >  local cursor = zettels[current_zettel_id].data:len()+1
     >  local quit = false
     >  curses.curs_set(1)
     >  while not quit do
@@ -2482,7 +2482,7 @@
     >  end
     >  local y, x = top, left + 1  -- left padding; TODO: indent
     >  window:mvaddstr(y, x, '')
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    if i == cursor then
     >      cursor_y = y
     >      cursor_x = x
@@ -2744,12 +2744,12 @@
     >    {'^l', 'line>>'},
     >    {'^k', 'del to line>>'},
     >  }
-    >  local old_data = string.sub(zettels[current_zettel_id].data, 1)
+    >  local old_data = zettels[current_zettel_id].data:sub(1)
     >  local top = (render_state.curr_h - 1) * (view_settings.height + view_settings.vmargin)
     >  local bottom = top + view_settings.height
     >  local left = (render_state.curr_w - 1) * (view_settings.width + view_settings.hmargin)
     >  local right = left + view_settings.width
-    >  local cursor = string.len(zettels[current_zettel_id].data)+1
+    >  local cursor = zettels[current_zettel_id].data:len()+1
     >  local quit = false
     >  curses.curs_set(1)
     >  while not quit do
@@ -2791,7 +2791,7 @@
     >      cursor = cursor-1
     >    end
     >  elseif key == 12 then  -- ctrl-l
-    >    local max = string.len(prose)
+    >    local max = prose:len()
     >    while cursor <= max and prose[cursor] ~= '\n' do
     >      cursor = cursor+1
     >    end
@@ -2799,7 +2799,7 @@
     >  elseif key == 2 then  -- ctrl-b
     >  -- delete
     >  elseif key == 11 then  -- ctrl-k
-    >    while cursor <= string.len(prose) and prose[cursor] ~= '\n' do
+    >    while cursor <= prose:len() and prose[cursor] ~= '\n' do
     >      prose = prose:remove(cursor)
     >    end
     >  -- exit
@@ -2848,33 +2848,33 @@
     >    end
     >  elseif key == 12 then  -- ctrl-l
     >    -- to end of line
-    >    local max = string.len(prose)
+    >    local max = prose:len()
     >    while cursor <= max and prose[cursor] ~= '\n' do
     >      cursor = cursor+1
     >    end
     >  elseif key == 6 then  -- ctrl-f
     >    -- to next word
-    >    local max = string.len(prose)
-    >    while cursor <= max and string.match(prose[cursor], '%w') do
+    >    local max = prose:len()
+    >    while cursor <= max and prose[cursor]:match('%w') do
     >      cursor = cursor+1
     >    end
-    >    while cursor <= max and string.match(prose[cursor], '%W') do
+    >    while cursor <= max and prose[cursor]:match('%W') do
     >      cursor = cursor+1
     >    end
     >  elseif key == 2 then  -- ctrl-b
     >    -- to previous word
-    >    if cursor > string.len(prose) then
-    >      cursor = string.len(prose)
+    >    if cursor > prose:len() then
+    >      cursor = prose:len()
     >    end
-    >    while cursor > 1 and string.match(prose[cursor], '%W') do
+    >    while cursor > 1 and prose[cursor]:match('%W') do
     >      cursor = cursor-1
     >    end
-    >    while cursor > 1 and string.match(prose[cursor], '%w') do
+    >    while cursor > 1 and prose[cursor]:match('%w') do
     >      cursor = cursor-1
     >    end
     >  -- delete
     >  elseif key == 11 then  -- ctrl-k
-    >    while cursor <= string.len(prose) and prose[cursor] ~= '\n' do
+    >    while cursor <= prose:len() and prose[cursor] ~= '\n' do
     >      prose = prose:remove(cursor)
     >    end
     >  -- exit
@@ -2906,7 +2906,7 @@
     >  end
     >  local y, x = top, left + 1  -- left padding; TODO: indent
     >  window:mvaddstr(y, x, '')
-    >  for i=1,string.len(s) do
+    >  for i=1,s:len() do
     >    if i == cursor then
     >      cursor_y = y
     >      cursor_x = x