Please note that your syntax for opening files works, but is somewhat obsolete. It is better to use the three-argument syntax and to use lexical filehandles. Something like this:

my $infile = "master.cfg";
open my $FH, "<", $infile or die "could not open $infile $!";
[download]

You of course have to adapt other places of your code where you use the filehandles (to use $FH instead of FH).