I had the same problem and just fixed it! The problem is the initial assignment of the variables.

e.g.

my $status = $myhash{'key1'};
$status =~ s/\t/    /g;
[download]

will give an error IF the value of $myhash{'key1'} is not defined.

This was my fix:

my $status = $myhash{'key1'} || '';
$status =~ s/\t/    /g;
[download]

no more error!