##
02,sometext2
03,sometext3
05,sometext5
10,sometext10
####
open(IN,"in.txt");
while()
{
if($_=~m/^\n/)
{
$tell_val=tell();
}
if($_=~m/^\d+/)
{
$has{$&}=$tell_val if($tell_val ne '');
}
}
open(OUT,">output.txt");
foreach(sort{$a<=>$b}(keys %has))
{
seek(IN,$has{$_},0);
$line=;
print OUT $line;
print $_;
}