Help with PERL, simple commands, loops?

[Bob]

let's say you have 500 letters, and you wanted to know how many groups of 5 there are in the 500 characters. (500 divided by 5... i.e. answer should result to 100). I believe you need to use loops, but I am not getting it right... any help?

essentially it breaks down into having the command first identify all of the groups of 5, then printing them all

thanks!