for my $i (1 .. 1) 
{ 
    $arab_string .= "my \@arab$i = ("; 
    $blast_run = "blastn ATH1_chr$i.1con.01222004 $seq_file_name - +warnings"; 
    warn "$blast_run\n"; 
    $blast_output = `$blast_run`; 
    warn "Error: $!\n";
    ...