Thanks for your response, haukex. I'm not quite sure what you mean with reference to the "system package manager." I find no GUI equivalent of Ubuntu's "synaptic package manager." I prefer to get things done on the command line with *nix. (My windows preference is the opposite, but I prefer not to use Windows.) I wonder if you mean something like dpkg. As it is, I used

, and then I was unstuck. Would this be an instance of using the "system package manager," as you mean it?

Update: After fighting with the same install on my droplet, I realize there were other headers that needed to be installed by the system:

 
sudo apt install zlib1g zlib1g-dev
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The droplet had the former but not the latter, and it seems to make a difference.

I think that's really solid advise for an rpi. I proceeded as you outline, forsaking sudo cpan, and with the addition of this command:

cpanm has generally worked very well for my needs. I do have a sticky wicket, where I can't get cpanm to find dependencies:

$ ls
requires1.pm
$ cpanm --verbose --installdeps .
cpanm (App::cpanminus) 1.7044 on perl 5.028001 built for arm-linux-gnu
+eabihf-thread-multi-64int
...
--> Working on .
Entering /home/pi/Documents/curate/req
Configuring /home/pi/Documents/curate/req ... N/A
! Configuring . failed. See /home/pi/.cpanm/work/1647208802.16932/buil
+d.log for details.
Expiring 16 work directories.
$ cat requires1.pm 
package requires1.pm;

requires 'AnyEvent::AIO' => '1.1';
requires 'Async::Interrupt' => '1.24';
requires 'Cookie::Baker::XS' => '0.09';
requires 'Device::Firmata' => '0.65';
requires 'Device::SerialPort' => '1.04';
requires 'Device::WebIO' => '0.022';
requires 'Device::WebIO::Dancer' => '0.004';
requires 'Device::WebIO::Firmata' => '0.002';
requires 'Device::WebIO::RaspberryPi' => '0.900';
requires 'DBD::SQLite' => '1.58';
requires 'DBI' => '1.641';
requires 'Guard' => '1.023';
requires 'GPS::NMEA' => '0.17';
requires 'Math::Round' => '0.07';
requires 'RPi::WiringPi' => '2.3628';
requires 'RPi::Pin' => '2.3606';
requires 'Plack::Handler::Twiggy' => '0.1025';
requires 'Starman' => '0.4014';
requires 'Time::HiRes' => '1.9758';
requires 'WWW::Form::UrlEncoded::XS' => '0.25';
1;
$
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I couldn't get cpanm to find modules in typical perl .pl scripts, so I herded the requires into a barebones module in its own directory. I don't know how to serve it up any better than that.(?)

Your link for setting up rpi's has proved very useful indeed, giving me much more on my plate to come up to speed on. I'm happy to report that I think I have my first fail2ban implementation:

$ sudo fail2ban-client status sshd
Status for the jail: sshd
|- Filter
|  |- Currently failed:    0
|  |- Total failed:    0
|  `- File list:    /var/log/auth.log
`- Actions
   |- Currently banned:    0
   |- Total banned:    0
   `- Banned IP list:    
$
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Regarding section 5,

Crontab to broadcast RPi's address and name
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What is the purpose of doing this? Would this cause you to be indexed by search engines, or is it all within 50 yards (meters for bliako)?

crontab -e

@reboot hostname | socat -s - UDP-DATAGRAM:255.255.255.255:12340,broad
+cast 2>/dev/null * * * hostname | socat -s - UDP-DATAGRAM:255.255.255
+.255:12340,broadcast 2>/dev/null
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Can you break this up into parts? I've used crontab once, so that syntax with all the asterisks is familiar. I read that

runs it in sloppy mode, and I understand the syntax for sending stderr to the bitbucket.

I haven't cottoned onto it yet, even fiddling with  udplisten.pl

I have run:

$ sudo  ufw allow in 12340/udp
Rule added
Rule added (v6)
$
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, and was astonished to get somewhere in the debugger with it:

$ pwd
/home/pi/Documents/curate/req
$ ls
1.udplisten.pl  requires1.pm
$ perl -d 1.udplisten.pl -e '/HELLO xyZ129/'

Loading DB routines from perl5db.pl version 1.53
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(1.udplisten.pl:77):    $Getopt::Std::STANDARD_HELP_VERSION = 1;
  DB<1> b 86                                                          
+          
  DB<2> c                                                             
+          
main::(1.udplisten.pl:86):    my $RXSZ = $opts{b}//1024;
  DB<2> p $EXPR                                                       
+          
/HELLO xyZ129/
  DB<3> c                                                             
+          

192.168.red.acted
Debugged program terminated.  Use q to quit or R to restart,
use o inhibit_exit to avoid stopping after program termination,
h q, h R or h o to get additional info.
  DB<3>                                                               
+          

  DB<3> save 1.udp.txt                                                
+          
commands saved in 1.udp.txt
  DB<4> q                                                             
+          
$
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, with another terminal, doing:

echo "HELLO xyZ129" | socat - UDP-DATAGRAM:255.255.255.255:12340,broad
+cast
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sudo apt-get build-dep libnet-ssleay-perl
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I used this with my droplet in the cloud.

I sure like cpanm too when I finally get the thing kickstarted.

I always need to do this, too.

Again, thanks for your comments. Gruss aus Amiland,