Do you have some kind of resilence if STDLOG is not set up from the using script?

As I said, STDERR (via Carp croak() and cluck() ) mostly serves my purposes, but for sake of demonstration:

Given Logndebug.pm:

package Logndebug;
use strict;
use warnings;
use Exporter;

our @ISA = qw[ Exporter ];
our @EXPORT = qw[ LOG DEBUG logging ];

sub LOG {
    return unless fileno( *STDLOG );
    print STDLOG @_;
}

sub DEBUG {
    return unless fileno( *STDDBG );
    print STDDBG @_;
}

sub logging {
    my( $logging, $debugging ) = @_;
    *STDLOG = *{ $logging }   if defined $logging   and fileno( $loggi
+ng );
    *STDDBG = *{ $debugging } if defined $debugging and fileno( $debug
+ging );
}

1;
[download]

And SillyVec3D.pm:

package SillyVec3D;
use strict;
use warnings;
use Logndebug;

sub new {
    my $class = shift;
    my $self = bless { @_ }, $class;
    for my $attr ( keys %{ $self } ) {
        no strict 'refs';
        eval qq[
            *{ $attr } = sub {
                LOG( "$attr called with [\@_]" );
                my \$self = shift;
                DEBUG( "$attr set to: ", \$self->{ $attr } = shift ) i
+f \@_;
                \$self->{ $attr };
            }
        ];
    }
    return $self;
}

1;
[download]

And t-SillyVec3D.pl:

#! perl -slw
use strict;
use SillyVec3D;

our( $LOG, $DBG );

SillyVec3D::logging(
    $LOG ? *STDERR : undef,
    $DBG ? *STDERR : undef,
);

my $o = SillyVec3D->new(
   X => 1, Y => 2, Z => 3
);

print $o->X, $o->Y, $o->Z;

$o->X( 4 );
$o->Y( 5 );
$o->Z( 6 );

print $o->X, $o->Y, $o->Z;
[download]

In use:

C:\test>t-SillyVec3D
123
456

C:\test>t-SillyVec3D -LOG
X called with [SillyVec3D=HASH(0x32cf38)]
Y called with [SillyVec3D=HASH(0x32cf38)]
Z called with [SillyVec3D=HASH(0x32cf38)]
123
X called with [SillyVec3D=HASH(0x32cf38) 4]
Y called with [SillyVec3D=HASH(0x32cf38) 5]
Z called with [SillyVec3D=HASH(0x32cf38) 6]
X called with [SillyVec3D=HASH(0x32cf38)]
Y called with [SillyVec3D=HASH(0x32cf38)]
Z called with [SillyVec3D=HASH(0x32cf38)]
456

C:\test>t-SillyVec3D -DBG
123
X set to: 4
Y set to: 5
Z set to: 6
456

C:\test>t-SillyVec3D -LOG -DBG
X called with [SillyVec3D=HASH(0x8cf48)]
Y called with [SillyVec3D=HASH(0x8cf48)]
Z called with [SillyVec3D=HASH(0x8cf48)]
123
X called with [SillyVec3D=HASH(0x8cf48) 4]
X set to: 4
Y called with [SillyVec3D=HASH(0x8cf48) 5]
Y set to: 5
Z called with [SillyVec3D=HASH(0x8cf48) 6]
Z set to: 6
X called with [SillyVec3D=HASH(0x8cf48)]
Y called with [SillyVec3D=HASH(0x8cf48)]
Z called with [SillyVec3D=HASH(0x8cf48)]
456
[download]

You get logging and tracing embedded in the package, with minimal impact when turned off, and controlled from the calling script that can send the output wherever it choses with a single call on a package by package basis.

And if you set logging/debug on by passing in tied filehandles, they can add whatever boilerplate you desire.