Perl Grade Calculator

#########################
#       PERL TIPS       #
#########################
=begin comment
1 WYSWYG  strings (split across multiple lines)
2 Single brackets dont process symbols (\n), just shows them
3 Variable symbols for DECLARATION
    **for interpretation use $ for all***
        Scalar(simple)      '$'
        Array               '@'
        Hash/value pairs    '%'
4 print doesnt need ()
=cut


#########################
#   Grade Calculator    #
#########################

use Switch;             #cpanm package

print ("\n\tEnter your score: ");

#Global variable
$score = <STDIN>;       #get user input
chomp $score;           #remove newline char

print "\n Your grade:  ",gradeCalc(),"\n";


# Converts numeric score to letter grade
#
sub gradeCalc{
    my $grade;          #local variable

    switch ($score){
        case [90..100]{ $grade= "A"; }
        case [80..89] { $grade= "B"; }
        case [70..79] { $grade= "C"; }
        case [60..69] { $grade= "D"; }
        else          { $grade= "F"; }
    }

    return $grade;
}

<STDIN>;