use Guard qw(scope_guard);

sub ssh_execute_and_check {
  my $ssh = shift;
  my ($ret, $err) = $ssh->execute(@_);
  if ( $err or $ret =~ /Unknown command:/m ) {
      MyErr->throw({err => $err, ret => $ret, args => [@_]});
  }
  return $ret;
}

sub foo {

   $ssh->start_session($ssh_host) or MyErr->throw(...);

   scope_guard {
       $ssh->exit_session;
       $ssh->close_session;
   };

   my $ret1 = ssh_execute_and_check($ssh, 'command1', 'expect1');
   my $ret2 = ssh_execute_and_check($ssh, 'command2', 'expect2');

   ...
  
   1;
}