Regarding the first error (uninitialized value in concatenation at line 56), the previous replies are good, and I can suggest some other ways to do what you want:

# like this:

(my $newfile = $filename ) =~ s{.*[\\/]}{};
    # if there is no (back)slash, $newfile will be same as $filename

# or like this:

my @path = split /[\/\\]/, $filename;
my $newfile = pop @path;

# or use File::Basename, if that's appropriate to your needs
[download]

As for the second error (readline() on unopened filehandle at ... line 57) I would guess that line 57 is this one:

while(<$filename>) {
[download]

You are supposed to put an open file handle inside the "diamond" operator -- not a scalar string that holds the file name. Do something like this instead:

open( IN, $filename ) or die "$filename: $!";
while (<IN>) {
[download]