Also, if you want to return the output of the channel, the docs say it acts like a tied filehandle, so......

#!/usr/bin/perl
use warnings;
use strict;
use Net::SSH2;

my $ssh2 = Net::SSH2->new();

$ssh2->connect('localhost') or die "Unable to connect Host $@ \n";
$ssh2->auth_password('z','ztester') or die "Unable to login $@ \n";

#works 
#my $sftp = $ssh2->sftp(); 
#my $fh = $sftp->open('/etc/passwd') or die; 
#print $_ while <$fh>; 

# A channel object is created by the Net::SSH2 "channel" method.   
# As well as being an object, it is also a tied filehandle. 

my $chan = $ssh2->channel();
$chan->exec('ls -la');

while (<$chan>){ print }
[download]