I'd start with error checking. (added: Fletch is more accurate than I am on the functions you'll want to check errors on, consider adding similar error checking to the functions mentioned):
open( my $in, ">>".$seq_dir."/".$fa) or die "Unable to open $seq_dir/$fa for append: $!\n";
Obviously if the file is read only or the path isn't parsed correctly, the open call will fail and you won't be able to write to the file.

In reply to Re: appending to a file by Nkuvu
in thread appending to a file by lomSpace

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