|   `-- rev1
         |   |    `-- rev1.html
         |   `-- rev2
         |       `-- rev1.html

##</code><code>##

#!/usr/bin/perl
use strict;

while (<DATA>) {
  if (/rev_(\d)+/) { # what does this match ?
    print "'$1' matched in $_";    
  }
}
__DATA__
    `-- added
    |-- add.txt
    `-- added1
        |--action
        |   |-- action.txt
        |   `-- rev1
        |   |    `-- rev1.html
        |   `-- rev2
        |       `-- rev1.html

        `-- add.html