OK, that looks normal, except for the channel open failure. This is an error indication from the SSH server you are connecting to. You should investigate the server for clues, including any logs it produces. You should find an explanation there.

What ssh server are you connecting to and what operating system is it running on?

If you don't need a pseudo terminal (pty) you might try added use_pty => 0 to your options to Net::SSH::Perl->new(). There is a comment in the source code that support for pty is experimental. Maybe it doesn't work with some servers. You don't need a pseudo terminal to run an ls command.