This document discusses modulinos, which are files that can work as both programs and modules. It provides examples of a hello.pl file that outputs "Hello World" both when run directly and when used as a module. It then shows how to add unit tests to the file and make the output customizable by passing arguments. The key aspects are running code directly or via require, adding tests, and connecting command line arguments to object initialization.

1. ★ Advanced
Modulinos
brian d foy
The Perl Review
YAPC::NA 2012

2. Files that work as
programs and modules
at the same time

3. Unit testing
Code reüse
Distribution

4. # hello.pl
use v5.10;
say 'Hello World!';

5. % perl hello.pl
Hello World!

6. STDIN $0 STDOUT
@ARGV
%ENV exit code

7. Starting

8. use v5.10;
run();
sub run {
say 'Hello World!';
}

9. % perl hello.pl
Hello World!
% perl -e 'require q(hello.pl)'
Hello World!

10. # Hello.pm
use v5.10;
run() unless caller;
sub run {
say 'Hello World!';
}
_ _PACKAGE_ _

11. % perl Hello.pm
Hello World!
% perl -MHello -e 1
%

12. package Hello;
use v5.10;
__PACKAGE__->run
unless caller;
sub run {
say 'Hello World!';
}
_ _PACKAGE_ _

13. use Test::More;
use Test::Output;
use_ok( 'Hello' );
stdout_ok(
sub { Hello->run() },
"Hello World!n", ...
);

14. package Hello;
use v5.10;
_ _PACKAGE_ _->run
unless caller;
sub run {
my( $self ) = @_;
say { $self->fh }
'Hello World!';
}

15. package Hello;
use v5.10;
...;
sub fh { *STDOUT }

16. use Test::More;
use_ok( 'Hello' );
our $string;
{
open my $fh, '>', $string;
*Hello::fh = sub { $fh };
}
Hello->run;
is($string, "Hello World!n");

17. package Hello;
use v5.10;
...;
BEGIN {
my $fh = *STDOUT;
sub fh { $fh }
sub set_fh {
$fh = ...;
}
}

18. use Test::More;
use_ok( 'Hello' );
open my $fh, '>', my $string;
Hello->set_fh( $fh );
Hello->run;
is($string, "Hello World!n");

19. % perl hello.pl
Hello World!
% perl hello.pl Chicago
Hello World!
% perl hello.pl -m Rahm
Hello World!
% perl hello.pl < aldermen
Hello World!

20. Connect the
command line to new()
% hello.pl -s Houston
?
use Hello;
new()
my $app->new(
input => $in_fh,
output => $out_fh,
message => $message,
);
$app->greet;

21. sub run {
my( $class, @args ) = @_;
my %args =
$class->process_args(@args);
my $self = $class->new(%args);
say { $self->fh }
$self->message;
}

22. sub process_args {
require Getopt::Std;
local @ARGV = @_;
getopts('oim:', my %opts);
$opts{'o'} //= *STDOUT;
$opts{'i'} //= *STDIN;
$opts{'m'} //= 'Hello World!';
# left over @_?
my %args = map {
$opts_map{$_} => $opts{$_}
} keys %opts;
}

23. $app->new(
input_fh => $in,
output_fh => $out,
message => 'Hello World!'
);

24. sub new {
my( $class, %args ) = @_;
my $self = bless {}, $class;
foreach ( keys %args ) {
# maybe more complicated
$self->set( $_, $args{$_} );
}
return $self;
}

25. Stopping

26. #!perl
...;
...;
...;
exit(0);

27. sub run {
my( $class, @args ) = @_;
my $object = eval {
...;
Result->new( code => 0 );
} or $@;
exit( $object->code );
}

28. sub some_sub {
...;
die
Result->new( code => 15 );
...;
}

29. sub run {
my( $class, @args ) = @_;
my $object = eval {
...;
Result->new( code => 0 );
};
exit( $error_object->code );
}

30. Testing

31. run() unless caller;

32. UNITCHECK {
if($ENV{TEST_HARNESS}){
__PACKAGE__->run_tests;
}
elsif( ! caller ) {
__PACKAGE__->run;
}
}

33. Docs

34. UNITCHECK {
if($ENV{TEST_HARNESS}){
__PACKAGE__->run_tests;
}
elsif($ENV{PERLDOC}){
__PACKAGE__->show_docs;
}
elsif( ! caller ) {
__PACKAGE__->run;
}
}