PrimarySeq validation speedup

Small optimization to make validation of sequences faster:
  ~9 % faster for large sequences (10 Mbp)
  ~27% faster for small sequences (100 bp)

Bio/PrimarySeq.pm

@@ -324,20 +324,18 @@ sub _set_seq_by_ref {
            sequences are considered valid.
  Returns : 1 if the supplied sequence string is valid, 0 otherwise.
  Args    : - Sequence string to be validated
-           - Boolean to throw an error if the sequence is invalid
+           - Boolean to optionally throw an error if the sequence is invalid
 
 =cut
 
 sub validate_seq {
     my ($self, $seqstr, $throw) = @_;
-    $seqstr = '' if not defined $seqstr;
-    $throw  = 0  if not defined $throw ; # 0 for backward compatiblity
-    if ( (CORE::length $seqstr > 0         ) &&
-         ($seqstr !~ /^([$MATCHPATTERN]+)$/) ) {
+    if ( (defined $seqstr                ) &&
+         ($seqstr !~ /^[$MATCHPATTERN]*$/) ) {
         if ($throw) {
             $self->throw("Failed validation of sequence '".(defined($self->id) ||
-            '[unidentified sequence]')."'. Invalid characters were: " .
-            join('',($seqstr =~ /([^$MATCHPATTERN]+)/g)));
+                '[unidentified sequence]')."'. Invalid characters were: " .
+                join('',($seqstr =~ /[^$MATCHPATTERN]/g)));
         }
         return 0;
     }

t/Seq/PrimarySeq.t

@@ -7,7 +7,7 @@ use Data::Dumper;
 BEGIN {
     use lib '.';
     use Bio::Root::Test;
-    test_begin( -tests => 177 );
+    test_begin( -tests => 178 );
 
     use_ok('Bio::PrimarySeq');
     use_ok('Bio::Location::Simple');
@@ -366,10 +366,11 @@ is $seq->validate_seq( 'ACGT'   ), 1;
 is $seq->validate_seq( 'XFRH'   ), 1;
 is $seq->validate_seq( '-~'     ), 1; # gap symbols
 is $seq->validate_seq( '-.*?=~' ), 1; # other valid symbols
+is $seq->validate_seq( '0'      ), 0;
 is $seq->validate_seq( 'AAAA$'  ), 0;
-is $seq->validate_seq( 'tt&tt'  ), 0;
+is $seq->validate_seq( 'tt&t!'  ), 0;
 
-throws_ok { $seq->validate_seq('tt&tt', 1); } qr/.+/;
+throws_ok { $seq->validate_seq('tt&t!', 1); } qr/.+/;
 
 
 # Test direct option (no sequence validation)