More on the undefined variables problem. Would adding something like this do a loop be correct.

while ($line0=<>) {$line1=<>;$line2=<>;$line3=<>;
last if not defined $line0;
last if not defined $line1;
last if not defined $line2;
last if not defined $line3;
do_some_stuff;
}
[download]

Could I use some OR statements to get these last if-s on a single line. Or can or and and statements used only between two values. I was thinking like

 last if not defined $line0or$line1or$line2or$line3

or

 last if not defined $line0||$line1||$line2||$line3