I do most of my development work in BBEdit, which thankfully now supports Language Server Protocol and specifically PLS, a Perl implementation thereof. Near as I can tell, everything is set up properly for PLS to do its magic, but I cannot seem to get it to ever flag erroneous code or anything of that nature. Is there some way to run a debug mode on PLS to see if it is even working? I'm not sure if the problem lies in BBEdit or PLS at present and would like to try to narrow down the issue.
I followed the steps outlined on the BBEdit site and the GitHub page for the PLS CPAN module, including installing cpanm and then using cpanm to install PLS. The only issue I ran into IO::Async had trouble building and I had to use cpanm --force IO::Async ahead of cpanm PLS in order to install everything. This is, obviously given that I'm using BBEdit, running on macOS (12.3.1 on an M1 Max).
For the benefit of future readers: in your case the file(s) you were working on were located on a remote SFTP server and opened using BBEdit's built-in SFTP support.
LSP, and BBEdit's support thereof, requires that files be stored on a local file system. (If you wanted, you could use ExpanDrive or a similar tool to mount a remote server as a file system. It would probably be pretty slow, though.)