Since others have so competently answered your original question, I'll just pick on the rest. :)

### *Always* check the return when you open a file!
# open (FH3, ">lessons.txt");
open FH3, ">lessons.txt" or die "lessons.txt: $!\n";

        print FH3 "Perl*Lesson1\n";
        print FH3 "Perl*Lesson2\n";
        print FH3 "Perl*Lesson3\n";
        print FH3 "Java*Lesson1\n";
        print FH3 "Java*Lesson2\n";
        print FH3 "Java*Lesson3\n";
        print FH3 "PHP*Lesson1\n";
        print FH3 "PHP*Lesson2\n";
        print FH3 "PHP*Lesson3\n";

### Lots of wasted typing, there. Doing it as a single line was OK - o
+r
### you could use a 'heredoc'.

print FH3 <<'Text_Block';
Perl*Lesson1
Perl*Lesson2
[etc...]
Text_Block

### Or you could even generate it - since it's all repetitive.
for my $lng (qw/Perl Java PHP/){ print "$lng*Lesson$_\n" for 1..3 };
[download]

-- 
Human history becomes more and more a race between education and catastrophe. -- HG Wells