my @xx = ['A',1,['B',2,3,4],5,['C',6,['D',7,8,9]]];

traverse("", @xx);

sub traverse {
  my $d = $_[0] . "/" . $_[1][0];
  for my $i (1 .. @{$_[1]}-1) {
    if (ref $_[1][$i] eq 'ARRAY') {
      traverse($d, $_[1][$i]);
    } else {
      print $d . "/" . $_[1][$i] . "\n";
    }
  }
}

##</code><code>##

/A/1
/A/B/2
/A/B/3
/A/B/4
/A/5
/A/C/6
/A/C/D/7
/A/C/D/8
/A/C/D/9

##</code><code>##

Can't use string ("A") as an ARRAY ref while "strict refs" in use at test.pl line 6