string.gsub help
 

Hello, help me with regular expressions.
How to make that at the beginning of the word and after each 3 symbols was "!" ?

Example: !Hel!lo !Wor!ld. !Tes!t !lua!.

thx.

I can see this as a series of 3 string.gsub() calls:
The first call processes splitting the words into groups of 3 letters separated by "!". This needs to be done first as the other replacements will screw up the grouping pattern. The second pattern handles the start of words by inserting the separator between any occurrence of a space followed by a non-space. The third handles an exception that would rise when the string starts with a non-space character.