use Bio::FASTASequence;

my $fasta = ">sp|P01815|HV2B_HUMAN Ig heavy chain V-II region COR - Homo sapiens (Human).
QVTLRESGPALVKPTQTLTLTCTFSGFSLSSTGMCVGWIRQPPGKGLEWLARIDWDDDKY
YNTSLETRLTISKDTSRNQVVLTMDPVDTATYYCARITVIPAPAGYMDVWGRGTPVTVSS
";

my $object = Bio:FASTASequence->new( $fasta );
my $sequence = $object->getSequence;