It seems SearchIO failed to parse your file.

Furthermore, I've found several questions, in:

my $in = new Bio::SearchIO(-format => 'blast',
                           -file   => ">".$maid_dir."\\".$maid."aln_hu
+.aln",
                           -report_type => 'blastn');
[download]

1: Are you sure you are reading a BLAST file, while your file extension is "aln", which seems to be a multiple sequence alignment?

2: Are you sure you need "-report_type"? In the documentation, it says only if you're reading a blast2seq result, you need to use that