>Seq1
AGAGAGAGAGAGGA
AGAGAGAGTTCCTT
CATCGCACATCAGA
AGG
>Seq2
GCGTGAGATTGAGG
GAATTGAGAGAGAG
>Seq3
GAGAGCGCGACCCC
TGAGTAGATAGAGA
ACAGATATAGGAGA
AGAG


##</code><code>##

#Print the file
print $_.$/ for (@fastafile);

#Reverse the file
@fastafile = reverse @fastafile;

#Change the 2nd secuence
$fastafile[1] = $other_seq;

#Put more sequences
push @fastafile, $other_seq;


##</code><code>##

tie @fastafile,'Tie::File',recsep=>"\n>",autochomp=>1;