use LWP::Simple;
foreach $ID (@ID) {
 $content=" ";
 $url="http:://...docid=$ID";
 $content=get($url);
 # subsequently I extract information from the string  
 # $content, which only serves as a contemporary storage 
 Open FILE, ">> C:/perl/output.txt";
 Print FILE $content; 
 # actually it's all the other variables whose values I 
 # want to save
}