Chapter 2

types, it's not likely you'll be overloading addition in your modules. On the other 

hand, overloading conversion is quite common. An overloaded conversion 

operator is called when Perl wants to use your object in a particular context 

string, numeric, or Boolean.

Overloading string conversion enables you to provide a method that Perl will 

call when it wants to turn your object into a string. Here are a few examples of 

places where a string conversion operator is used:

$string = "$object";

$string = "I feel like a " . $fly . " with its wings dipped in honey.";

print "Say hello to my little ", $friend, ".\n";

Without an overloaded string conversion operator, objects are converted to 

highly esoteric strings such as  IO::File=GLOB(0x8103ee4)  just next door to 

useless. By providing a string conversion operator, a class can furnish a more 

useful string representation. This can enhance debugging and provide a simpler 

interface for some modules.

For example, one of my fellow BOA programmers is an exceptionally lazy indi 

vidual. He's responsible for the networking code in BOA::Network. Each network 

connection is represented as an object in the BOA::Network class. Since he's 

such a lazy guy, he'd like to be able to use the BOA::Logger class with the absolute 

minimum work:

$logger >write(1, $connection);

His initial suggestion was that I modify write() to check for BOA::Network objects 

and pull out the relevant status information for logging. That would work, but 

sooner or later you'd have an if() for every module in BOA. Because BOA is a big 

ol' application, this wouldn't be a good idea. Instead, BOA::Network can overload 

string conversion:

package BOA::Network;

use overload  ""  => "stringify";

sub stringify {

  my $self = shift;

  return ref($self) . " => read $self >{read_bytes} bytes, " .

         "wrote $self >{wrote_bytes} bytes at " .

         "$self >{kps} kps";

}

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