#1 slurping the whole thing in memory, and splice 
@file = <>;
splice @file, 0, 4;
print @file;

#2 using the flip-flop operator
while (<>){
  next unless $.>3 .. 1;
  #...
  print;
}

#3 another flip-flop
$start = -3;
while (<>){
  next unless $start++ .. 1;
  #....
  print;
}

#4 just repeat 4 times
$dummy=<> for 1..4;

#5 make it multifile proof
while (<>){
  close( ARGV) if (eof); 
 next unless $.>3 .. eof;
  #...
  print;
}