use URI;
my $x = 'http:/a.com/a/b/c/d/e.json?x=1&y=2';
my $y = '../../../';
my $u = URI->new($x);
my $p = $u->path().'/'.$y;
$u->path($p);
print $u;
<c>
<p>With this result: <c>http:/a.com/a/b/c/d/e.json/../../../?x=1&y=2