The Capture::Tiny module can be used to capture STDERR. For example, 
#!/usr/bin/env perl

use strict;
use warnings;
use Net::OpenSSH;
use Capture::Tiny ':all';

my $host = 'broken';
my $ssh;
my ($stdout, $stderr, @result) = capture {
    $ssh = Net::OpenSSH->new($host);
};

print "Captured STDERR: $stderr\n";

$ssh->error and die "Couldn't establish SSH connection: ". $ssh->error
+;

exit;

[download]
gives the output: 
Captured STDERR: ssh: Could not resolve hostname broken: nodename nor 
+servname provided, or not known

Couldn't establish SSH connection: unable to establish master SSH conn
+ection: master process exited unexpectedly at ns.pl line 15.

[download]

In reply to Re: Handling STDERR when using Net::OpenSSH by kevbot
in thread Handling STDERR when using Net::OpenSSH by mds

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