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print "Enter the student's course(s) ";
$self->{"Course(s)"}=[<STDIN>]

print "Enter the student's course(s) delimiting 
them with a comma (,) ";
...
 $cour =~ s/\s+//g;
 my @cour = split(",", $cour);
 chomp($self->{"Course(s)"}->{"cour"}=[@cour]);

sub add_courses {
  my $self = shift;
...
  for ($i=0; $i<$num; $i++) {
   push @{$self->{'Course(s)'}->{'cour'}}, $courses->[$i];
}

Here are the statistics for the Sino.
Address: kk
...
Tuition: kk
Course(s): Chem, Bio, Maths, C++, Java
After dropping: Chem, Bio, Maths, , Java

package Student3;
sub new { my $class = shift;
...
   join (", ", @{$self->{'Course(s)'}->{'cour'}}), "\n";
}
1;

#!/usr/bin/perl -w
use Student3;
...
$student1->add_courses(["C++", "Java"]);
$student1->show_student;
$student1->drop_courses(["C++"]);