Hi all

I have the string '1 20 3 400 5 60 7 800 9 0 ' and need to replace
every n-th space in the string with another character. So if n=2 and
the replacement character is '\n', then the above would become

'1 20\n3 400\n5 60\n7 800\n9 0\n'.

I'm sure it must be possible (easy, even) to do this with a regex
substitution, but unfortunately I'm no regex ninja.

So far I have:

'1 20 3 400 5 60 7 800 9 0 '.sub(/(\d* \d* )/) {|s| s + "\n"}
=> "1 20 \n3 400 5 60 7 800 9 0 "

But how do I get the substitution to be 'repeated'? Changing the regexp
to /(\d* \d*)*/ does not do what I want.

Also, I'm planning to run this on a large string, so I'd like it to be
efficient if possible.

Thanks in advance

C