#!/usr/bin/perl -w

use Cwd qw/getcwd realpath/;
use strict;

my %processed;
sub recursive {
	my $dirarg = shift;

	chdir $dirarg;
	my @results = map { chomp; realpath($_); } `ls $dirarg`;
	# ls is my example "vendor program" that returns files/dirs

	# prevent infinite recursion because of sym-links
	$processed{$dirarg} = 1;

	my @found = grep { -f } @results;          # get list of files
	foreach my $dir ( grep { -d } @results ) { # same for directories
		push @found, recursive($dir) unless($processed{$dir});
	}

	return @found;
}


sub queue {
	my @heap = ( shift );
	my %processed = ();

	while(-d $heap[-1]) {
		my $dir = pop @heap;
		next if $processed{$dir};

		chdir $dir;
		my @result = map { chomp; realpath($_); } `ls $dir`;
		$processed{$dir} = 1;
		unshift @heap, grep { -f } @result;
		push @heap, grep { -d } @result;
	}
	return @heap;
}

print join "\n", (recursive(getcwd()), "\n");
print join "\n", (queue(getcwd()), "\n");