#bi is population index
planet 'Taurus I' : bi+= 200+10*3 : system.scoutdata='Heavily armed'
system taurus : code { if ( scoutdata eq '' ) { owned=1 }  }

translated to:

$planet{'taurus i'}{'bi'}+= 200+10*3; 
$planet{'system'}{'scoutdata'}= 'Heavily armed';
if ($system{'taurus'}{'scoutdata'} eq '') { $system{'taurus'}{'owned'}=1; }