How do I stop these messages?

If they don't indicate an actual problem with your code you could try turning warnings off. If that doesn't work maybe eval the suspect lines, if you're sure that $host is valid:

die "Need a host" unless $host;
eval { $ssh = Net::SSH::Perl->new($host, protocol => 2) };
die "Something broke: $@" if $@; # if it matters
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Look inside the modules to see what's happening:

Net/SSH/Perl/SSH2.pm

Net/SSH/Perl/Channel.pm

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