use strict;

use vars qw/%PhoneBook/;

# Read in CSV phone book
ReadPhoneBookFile();

# Run two parameter tests
my $ValidTest = "8594";
my $InvalidTest = "9999";

print "Parameter test 1 - Number to find is: $ValidTest\n";
print 'The caller was: ', MatchPhoneNumber($ValidTest), "\n";

print "\nParameter test 2 - Number to find is: $InvalidTest\n";
print 'The caller was: ', MatchPhoneNumber($InvalidTest), "\n";

exit;


sub ReadPhoneBookFile
###
###  Reads in a CSV separated phone book, splits, stuffs details into a hash
###
###  In real-world script, data is read from an external file.
{
    foreach (<DATA>) {
        my @Details        = split(/,/,$_);
        $PhoneBook{$Details[0]} = $Details[1];
    }
}


sub MatchPhoneNumber
###
### Attempts to match the phone number with a name from the phonebook
### Either returns the caller name if number in hash or "Unknown caller".
###
{
    my $NumToFind = shift;

    return defined $PhoneBook{$NumToFind}
      ? $PhoneBook{$NumToFind}
      : 'Unknown Caller';
}

__DATA__
8594,Tom
9000,Dick
1234,Harry