perl - Reading in the First Line from a .txt File, Removnig it from the .txt., and Sliding all of the Other Lines Up by 1 Unit -

i have .txt file in each line 1 element. subject suggests, i'd input first row .txt. then, i'd remove .txt file i've inputted it. @ same time, i'd slide each element 1 row such former second row element becomes new first row.

i'm not quite sure how proceed beyond: open( $l, '<', 'input.txt' ) or die "can not open input.txt: $!";

use strict;  if ($#argv) {     print "\nusage: test.pl filename\n\n";     exit(); }  $f; if (open($f, $argv[0])) {     print scalar(<$f>);      $s = join('', <$f>);     close($f);      if (open($f, '>', $argv[0]))     {         print $f $s;         close($f);     } } else print "\ncan't open input file $argv[0]\n\n"; 

or sub

sub slidefile($) {     $filename = shift();      $f;     if (open($f, $filename))     {         <$f>;          $s = join('', <$f>);         close($f);          if (open($f, '>', $filename))         {             print $f $s;             close($f);         }     } }