Scrape files from Browser with perl script

my (@arg) = @ARGV;
#perl script to scrape the slides from browser all at once
if (!@arg){
    print "USAGE: \n
       First arg : SEMISTER Number
       Second Arg: Semister Subject
       Third arg : UNIT Number
       Fourth Arg : Number of Pages
       IMAGE TYPE : JPG or PNG 
       Example: perl $0 3 DIF233 UNIT2 49 jpg\n";
     exit;   
}else{
    #print "$arg[0]==$arg[1] === $arg[2]==$arg[3]\n";
    system("mkdir -p $arg[1]/$arg[2]"); #creates directory where you want to store the slides
    system("cd  $arg[1]/$arg[2];"); #path to that directory
   
    #my $val="(?:jpg|png)";
    my $val = $arg[3];
      for(my $i=0;$i<=$val;$i++){ #from 0 to the number of slides the ppt has
   
     my $val1= "wget http://media.msconline.au-kbc.org.in/slides/semester$arg[0]/$arg[1]/$arg[2]/slides/complete/img$i.jpg"; #scrapes the slides from browser
      my $val2= "convert img$i.jpg slide.pdf"; #converts all slides to one pdf
     my $val3= "mv slide.pdf '$arg[1]/$arg[2]/'"; #moves the pdf to the directory created
      system("$val1");
     system("$val2");
      system("$val3");
    }
    for(my $i=0;$i<=$val;$i++){
        $c = `pwd`; #the directory is from your present working directory
        chomp($c);
        $aa = "$c/$arg[1]/$arg[2]/";
       
        #print "cp img$i.png $aa\n";
    system ("mv img$i.jpg  $aa"); #moves the slides to the directory created

    }

#http://media.msconline.au-kbc.org.in/slides/semester3/DIF233/unit1/slides/complete/img{0..63}.png
#http://media.msconline.au-kbc.org.in/slides/semester3/DIF233/combined/img0.jpg   
#http://media.msconline.au-kbc.org.in/slides/semester3/DIF232/unit2/slides/complete/img8.html
#http://media.msconline.au-kbc.org.in/slides/semester3/DIF232/unit2/slides/complete/img8.png
#run as perl down.pl 4 DIF%20004 unit1 63
}