my $fh;
open($fh, "cat seqfile |") ||die $!;
my $seqio = Bio::SeqIO->new(-format => $seqformat, -fh => $fh);

# OR retrieve a sequence from the blast formatted db 'nt'
#    by GI number 

open(IN, "fastacmd -d nt -s 3264957 |") ||die $!;
my $seqio = Bio::SeqIO->new(-format => 'fasta',-fh => \*IN);
while( my $seq = $seqio->next_seq ) {
 #and so forth....
}