Someone

#!/usr/bin/perl -w
while (my $test = <STDIN>)
{
	chomp($test);
	@marks = split(/:/, $test);
	$mark{@marks[0]} = @marks[1];
}

print "Marks list (in marks order):\n";
for my $m (sort {$mark{$a} <=> $mark{$b} }
           keys %mark) {
     print "$m	=> $mark{$m}\n";
}

print "\n";

print "Marks list (in alphabetical order):\n";
for my $m (sort keys %mark) {
	print "$m => $mark{$m}\n";
}

print "\n";

print "Marks list (in reverse marks order):\n";
for my $m (sort {$mark{$b} <=> $mark{$a} }
           keys %mark) {
     print "$m	=> $mark{$m}\n";
}