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http://www.lua.org/manual/5.1/manual.html#5.4.1 https://www.gammon.com.au/scripts/doc.php?lua=string.find
escape special characters for pattern matching
pattern = pattern:gsub ("%+", "%%%+") -- change '+' to '%+' pattern = pattern:gsub("([+%?])", "%%%1") -- escape only characters from set pattern = pattern:gsub("([^%w])", "%%%1") -- escape all non alphanumeric characters