use CGI ':standard'; use File::Spec 'rel2abs'; my $ROOT = "/var/myapp/docroot/"; # wherever my $user_path = param('path'); # perhaps s/^\/+// also my $absolute = rel2abs($user_path, $ROOT); if ($absolute =~ /^\Q$ROOT/) { # $absolute is probably within $ROOT, so process it if (open(INF, "< $absolute")) { # it's here, do whatever } else { # "404 not found" } } else { # ERROR - They've tried to ../ their way out }