Help with LPeg

[Christopher Tallman <cjtallman@...>]

Hi, I'm trying to accomplish a string find/replace on a Lua file,
essentially updating the values stored in a table with new values,
while preserving the structure, layout, and comments of the file (I
don't want to just serialize the table, since that would drop
formatting and comments).

For example, let's say I have a file Lua file containing the following:

<code>
-- Range descriptions
ranges = {
  [1] = {0, 100}, -- primary
  [2] = {101, 500}, -- secondary
  [3] = {500,1000}, -- final range
}
</code>

I'm trying to write a lua program that will read in this file and the
values in the subtables with new values and write the file back out,
preserving the rest of the file.  I'm pretty sure this is a simple
problem to solve with LPeg, but I've never used it before.  I could
probably get this working with plain regex, but I would like to learn
something new in the process and try doing it with LPeg.  Any advice
or pointers on how I can get this to work?  Good resources for someone
unfamiliar with PEG?

Many thanks,
Chris