Shell Programming and Scripting

open(MY_FILE, $ARGV[0]) or die

$COUNTER = 1;
$LINE = <FILE>;
while ($LINE, <FILE>) {
# Adds leading zeros for numbers 1 digit long
   if ($COUNTER<10){
      print "000";
   }
   # Adds leading zeros for numbers 2 digits long
   if (($COUNTER>9) && ($COUNTER<100)){
      print "00";
   }
   # Adds leading zeros for numbers 3 digits long
   if (($COUNTER>99) && ($COUNTER<1000)){
   print "0";
   }
   # Prints line number and line
   print "$COUNTER: $LINE \n";
   $COUNTER += 1;
    }
    close FILE;

while ($LINE, <FILE>) {

while ($LINE = <FILE>) {

while (<>) { #<- opens @ARGV auto-magically
   printf "%04d: %s\n",$.,$_;
}