How to find the indexes or positions of a character which occurs multiple times?

[Ghoast 0]

I've made a bot which should insert a string of text into a block of text. I want it to insert the text after a random fullstop '.'

 

So far I've got this:

 

set(#blocktext - text from file

 

 

set(#blocktext, $insert text(#blocktext, ". {#stringtoinsert}", $find index(#blocktext, ".")), "Global")

 

This inserts my string after the FIRST fullstop in every block text..

 

However I want to randomize this and make it choose a random full stop to insert the string after.

 

After some hours of working on it I think a solution could be to return the indexes of all the full stops and then instruct ubot to choose a random position from these numbers to insert the string after..

 

Any ideas?