use File::Slurp;

my $out='';
while(<>)
{
  $out .= "1:$_";
}
$out .= "end1\n";
write_file("out1.txt", $out);

$out='';
while(<>)
{
  $out .= "2:$_";
}
$out .= "end2\n";
write_file("out2.txt", $out);