use Bio::DB::GenBank;
    $gb = Bio::DB::GenBank->new();

    $seq = $gb->get_Seq_by_gi('405830'); # GI Number
print $seq;

##</code><code>##

Bio::Seq::RichSeq=HASH(0xa49c0b4)

##</code><code>##

http://www.ncbi.nlm.nih.gov/nuccore/405830?report=fasta