if(! defined $opt_t) { &usage(); die "-E- Missing required title: -t <title>\n"; }
if(! defined $opt_o) { &usage(); die "-E- Missing required argument output video names: -o <output.mkv>\n"; }
if(! defined $opt_i) { &usage(); die "-E- Missing required argument input video names: -i <input,input,...>\n"; }
if(! defined $opt_t) { &usage(); die "-E- Missing required title: -t <title>\n"; }
if(! defined $opt_o) { &usage(); die "-E- Missing required argument output video names: -o <output.mkv>\n"; }
if(! defined $opt_i) { &usage(); die "-E- Missing required argument input video names: -i <input,input,...>\n"; }