#!/usr/bin/perl
use strict;
use warnings;
use Bio::SeqIO;

my $in  = Bio::SeqIO->new( -file   => "sample_gb.gb" ,
                           -format => 'GenBank');
my $out = Bio::SeqIO->new( -file   => '>fasta.dat',
                           -format => 'fasta');

while ( my $seq = $in->next_seq() ) {
	$out->write_seq($seq);
}