use strict;
use warnings;


my($filename) = "fasta.txt";

open(FILE, $filename);

while(<FILE>)
{
   my($line) =$_;
   if($line=~/^>/ and $line =~ /unknown/ )
   {
       my($header) =$line; 
       print $header;                             
       <FILE>;
       print $_; 

     }   
 }  
            
 close FILE;
 exit;