[Bioperl-l] question on installation

[Jiang Qian]

Hi,

I am new on BioPerl. I installed the system on a Linux machine through
the procedure of "perl Makefiel.PL" => "make" => "make test" => "make
install". Everything seems okay. But when I tried the script from
tutorial,

use Bio::Perl;
$seq_object = get_sequence('swissprot',"ROA1_HUMAN");
write_sequence(">roa1.fasta",'fasta',$seq_object);

I got the error message " Your system does not have IO::String installed
so the DB retrieval method is not available at
/usr/lib/perl5/site_perl/5.6.1/Bio/Perl.pm line 466
 Bio::Perl::get_sequence('swissprot', 'ROA1_HUMAN') called at
./try_bioperl.pl line 7".

What's the problem? Anyboday can help me with this? Thanks,

-Jiang