Hi! Thanks for explanation. Not sure If I understood all you told here. But what I already tried and here the results:

sshuttle -D ... 2>&- - hangs, when gets run by Perl script:

$ cat test.bash
/usr/sbin/sshuttle -v -D -r vagrant@127.0.0.1 192.168.0.0/24 2>&-
echo OK

$ cat capture-tiny.pl

use Capture::Tiny qw{tee};
tee {
  system('bash test.bash');
};

vagrant@Debian-jessie-amd64-netboot:~/my/IPC-sshutle-issue$ perl capture-tiny.pl
vagrant@127.0.0.1's password:
Connected.
OK
# hangs here

The same result (hangs) with sshutle -D ... 2>&- | cat

$ cat test.bash
/usr/sbin/sshuttle -v -D -r vagrant@127.0.0.1 192.168.0.0/24 2>&- | cat
echo OK

And the same result (hangs) with #$SIG{'TSTP'} = 'IGNORE';

$ cat capture-tiny.pl

$SIG{'TSTP'} = 'IGNORE';
use Capture::Tiny qw{tee};
tee {
  system('bash test.bash');
};

Probably I do something wrong?

PS. I have not succeed with IO:Pty script example yet, as it seems a bit complicated for me.