use WWW::Mechanize::Firefox;
use File::Copy;

# @list contains the list of links to pdf files
foreach $x (@list) {
    my $mech = WWW::Mechanize::Firefox->new(autoclose => 1);
    
    #This downloads the file using firefox in desired folder
    $mech->get($x);  
    
    opendir(DIR, "output/download");
    @FILES= readdir(DIR);
    my $old = "output/download/$FILES[2]";
    move ($old, $new);  # $new is the URL of the new filename
}