for each dir ( dirs) # I am using pseudo-code...:-)
  => if chdir(dir)

    => do smth. there
  => else
   ==> print_warning(couldn't go to dir, skipping)
......

##</code><code>##

die unless chdir($dir);

##</code><code>##

 if kind($matter) == "solid" {
   dig_it($matter); }
 eslif kind($matter) == "liquid" {
  die "We don't support underwater activities yet"; }
 else {
   die "RTErr: Unexpected type of matter!";}