Constructor method which accepts a reference to a hash array or a list of name => value parameters which are folded into a hash. The _init() method is then called, passing the configuration hash and should return true/false to indicate success or failure. A new object reference is returned, or undef on error. Any error message raised can be examined via the error() class method or directly via the $ERROR package variable in the derived class.

my $module = My::Module->new({ ... })
    || die My::Module->error(), "\n";

my $module = My::Module->new({ ... })
    || die "constructor error: $My::Module::ERROR\n";

May be called as an object method to get/set the internal _ERROR member or as a class method to get/set the $ERROR variable in the derived class's package.

my $module = My::Module->new({ ... })
    || die My::Module->error(), "\n";

$module->do_something() 
    || die $module->error(), "\n";

When called with parameters (multiple params are concatenated), this method will set the relevant variable and return undef. This is most often used within object methods to report errors to the caller.

package My::Module;

sub foobar {
    my $self = shift;

    # some other code...

    return $self->error('some kind of error...')
        if $some_condition;
}

Generates a debugging message by concatenating all arguments passed into a string and printing it to STDERR. A prefix is added to indicate the module of the caller.

package My::Module;

sub foobar {
    my $self = shift;

    $self->debug('called foobar()');

    # some other code...
}

When the foobar() method is called, the following message is sent to STDERR:

[My::Module] called foobar()

Objects can set an internal DEBUG value which the debug() method will examine. If this value sets the relevant bits to indicate DEBUG_CALLER then the file and line number of the caller will be appened to the message.

use Template::Constants qw( :debug );

my $module = My::Module->new({
    DEBUG => DEBUG_SERVICE | DEBUG_CONTEXT | DEBUG_CALLER,
});

$module->foobar();

This generates an error message such as:

[My::Module] called foobar() at My/Module.pm line 6

Returns the version number for a module, as defined by the $VERSION package variable.