# Munge the current line into what we want
    $line =~ s!^http://!url$counter=http://!i;
    $line =~ s!&!item=!g;
[download]

I think this should be

# Munge the current line into what we want
    $line =~ s!^http://!url$counter=http://!i;
    $line =~ s!&!item$counter=!g;
[download]

Otherwise, great post