use strict;

my (%PhoneBook,$TheCaller);
my ($ValidTest,$InvalidTest);
my ($name,$NumToFind);

# Read in CSV phone book
&ReadPhoneBookFile;

# Run two parameter tests
$ValidTest = "8954";
$InvalidTest = "9999";

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

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

# Run two direct tests.  
# First one works, second one doesn't.
print "\nDirect test 1 (8594) - ".$PhoneBook{8594};		# WORKS!

$NumToFind = "8594";
print "Direct test 2 (8594) - ".$PhoneBook{$NumToFind};	# DOES NOT WORK!

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.
{
	my ($Name,$Number,@Details);

	foreach (<DATA>)
	{
		@Details 	= split(/,/,$_);
		$Number		= $Details[0];
		$Name   		= $Details[1];

		$PhoneBook{$Number} = $Name;
	}
}


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;
	my $TheName;

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

	return $TheName;
}

__DATA__
8594,Tom
9000,Dick
1234,Harry