my $line = "DIQMTQSPSSLSASVGDRVTITCXXXXXXXXXXXWYQQKPGKAPKXXXXXXXXXXXGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCXXXXXXXXTFGQGTKVEIK";
my $pos=0;
while(my $pos_in=index($line,'XXXXXXXXXXX',$pos)>-1)
{
  print "feature $pos..$pos_in\n";
  $pos=$pos_in+11;
}
print "feature $pos..".length($line)."\n" if($pos<length($line));