one of ways to go: 
$/ = '>or';

sub{$h{$1} = $2 if /(\d+)\n\n(\w+)/}->() foreach <DATA>;

foreach (sort { $a<=>$b } keys %h){
        print ">or$_\n\n$h{$_}\n\n";
}


__DATA__
>or3

agagatgatagat

>or10

aacctttagtag

>or1

gtatatatata

>or2

tactacatgagg

[download]
output 
>or1

gtatatatata

>or2

tactacatgagg

>or3

agagatgatagat

>or10

aacctttagtag

[download]

In reply to Re: sorting headers in a file by Lennotoecom
in thread sorting headers in a file by utpalmtbi

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