it looks like $ssh is coming in undefined,

That doesn't happen with normal blessed objects:

#! perl -slw
use strict;
use threads;

package Test;

sub new{ bless [], $_[0] }
sub exec{ print 'exec method called from thread: ', threads->tid }

package main;

my $o = Test->new;
$o->exec;

async{
    $o->exec;
}->detach;

sleep 1;

$o->exec;

__END__
c:\test>tobj
exec method called from thread: 0
exec method called from thread: 1
exec method called from thread: 0
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Which probably means that there is some misbegotten code in Net::SSH2 that is attempting to make it "thread-safe".

The next thing to try is creating the ssh object inside the thread:

use threads;
use Net::SSH2;

async {
    my $ssh = Net::SSH2->new( ... );
    $ssh->scp_put($firmware[$antenna_type],'/tmp/fwupdate.bin');
    print "Upgrading firmware, this will take about 3 minutes.\n";
    my $chan = $ssh->channel();
    $chan->exec("/sbin/fwupdate -m\n");
    $chan->close;
}->detach;

...
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Again, that ought to work, but I have no way to test this speculation!

Yeah, does seem like that. Trying to redefine $ssh inside the thread yeilds:

Attempt to free non-existent shared string 'GEN0', Perl interpreter: 0
+x8990e48 at Configuration.pl line 41, <> line 3.
Segmentation fault
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If I try to completely make up a whole new connection like so:


        async {
            my $ssh2 = Net::SSH2->new();
            $ssh2->connect($host);
            $ssh2->auth_password($user,$password);
            print "Upgrading firmware, this will take about 3 minutes.
+\n";
            my $chan2 = $ssh2->channel();
            $chan2->exec("/sbin/fwupdate -m\n");
            $chan2->close;
        }->detach;
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I get this error:

Attempt to free non-existent shared string 'GEN0', Perl interpreter: 0
+x83f4e98, <> line 3.
Unbalanced string table refcount: (1) for "GEN0" during global destruc
+tion.
Unbalanced string table refcount: (1) for "/usr/share/perl/5.12/Symbol
+.pm" during global destruction.
Scalars leaked: -6
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This error is not fatal though but it apparently does not pass beyond this and my script hangs.