@gb = <GB>; #where GB is a guestbook html file
@gb2 = ("jsdjsjsj");
foreach $line(@bg){
  push(@gb2,$line);
  if($line =~ /INSERT_NEW_ENTRY/){
    push(@gb2,"<b>entry</b> $FORM{'whatever'}");
  }
}
seek(GB,0,0);
truncate(GB,0);
print GB @gb2;