This chunk of code:

# change normal array separator
my $foo = $";
$" = "\n";
print FH "@head";
$" = $foo;  # change back
[download]

could be replaced with:

{
 local $" = "\n";
 print FH "@head";
}
[download]

Using local removes the need for a temporary variable, as the saving and restoring of the previous value of the global $" variable is taken care of for you.

See local, the "Temporary values via local()" and "When to still use local()" sections of perlman:perlsub, and for a more detailed explanation and examples, see brother Dominus's Seven Useful Uses of local.

-sacked