use Path::Class;
# maybe $DIR is read from a configuration file or passed in from another tool
my $d = dir($DIR);
$d = $d->parent->subdir("bar"); # one "right" way to do path manipulation
my $p = $d=~/\/$/ ? "$d" : "$d/";

##</code><code>##

require File::Spec::Unix;
my $x = File::Spec::Unix->catdir('foo','bar').'/';