print "Start of my code\n";
my @array = `cmd to be executed`;
my $exit_status = $?;
print "Exit status is : $exit_status\n";
if ( $exit_status != 0) {
  print "Error in executing command : $! \n";
  exit;
}

##</code><code>##

Start of my code
Expired or invalid session token
Exit status is : 13312
Error in executing command : 

##</code><code>##

Start of my code
Exit status is : 13312
Error in executing command : Expired or invalid session token