package Foo;
my $dbh;

sub init_foo {
    my( %script_config )= @_;
    # Read config file
    ...
    # Connect to database
    $dbh ||= $config{ dbh } || connect_to_foo_database( %script_config );
    # Set up cache
    ...
};

##</code><code>##

sub frobnicate {
    my( $self, %options )= @_;
    $options{ dbh } ||= $self->get_dbh;
    ...
};

sub get_dbh {
    my( $self )= @_;
    $self->{ dbh } ||= do {
        DBI->connect( $self->{dbi_parameters} );
    };
};

##</code><code>##

package Module::MagicInit;
use strict;

my @init_queue;
sub register_init {
    push @init_queue, [ (caller(1))[2], @_ ];
};

sub init {
    for my $task (@init_queue) {
        my( $package, $callback, @args )= @$task;
        $callback->( @args ) or die "Init failed for $package.";
    };
};

##</code><code>##

package Foo;
use Module::MagicInit;

register_init( \&my_init, 'Hello', 'World' );

sub my_init {
    my( $greeting, $name )= @_;
    print "$greeting, $name\n";
};

1;

##</code><code>##

#!perl -w
use strict;
use Module::MagicInit;

...

Module::MagicInit::init();