FindBin correctly resolves it, giving us the full path to the directory.

As far as I understand, the OP wants the opposite, i.e. the respective symlink path being returned (/home/david/symlink in your case), not the target of the symlink, which is more generally aka realpath, and is easier to determine.

As ikegami pointed out, some other process (usually the shell) needs to keep track of the chdir history to be able to provide the info the OP wants.