sub dir_explorer
{
  my $entry = $_ ;
  if (-d $entry) { 
     ...  # ignore . and .. 
     opendir(DIR, $entry) or die "Can not open $entry: $!";
     # don't bother with "open(FILE, ">>$entry.tab")
     while ( defined( my $file = readdir DIR ) {
        if ( -f "$entry/$file" ) {
           textsformat( "$entry/$file" );
        }
        # now "$entry/$file.txt" should exist, so:
        system "cat $entry/$file.txt >> $entry.tab";
     }
     closedir DIR:
  }
}