Last time I did something like that, I ended up with code like this:

BEGIN {
  unless ($ENV{LD_LIBRARY_PATH} =~ m[:/some/path:])
  {
    $ENV{LD_LIBRARY_PATH} .= ':/some/path:';
    exec $^X, $0, @ARGV;
  }
}
[download]

I'm not sure it's the best way, but it worked.