Your code as posted does not compile.

The correct syntax would be:

 my %course =( "2CPR2B" => "C Language",
               "4PL400" => "Perl Language");
[download]

Now, to access the %course hash, you need to index it by a key. Hashes require the use of braces "{}" for indexing (aka subscripting). for example,

  print $course{"2CPR2B"}, "\n";
[download]

Would print out "C Language".

See List value constructors for more information on how to populate hashes, and extract from them.

The "subscripts" section of "perldoc perldata" has information on the syntax of hash subscripts.