Question

For simple output formatting I tend to use printf where I used write/format in the days of Perl 4. However sometimes it seems the simplest solution for variable numbers of output lines per data record. For example

#!/usr/bin/perl
use strict;
use warnings;

my ($lorem, $aprille);

format =
@# ^<<<<<<<<<<<<<<<<<<<<<<<< | ^<<<<<<<<<<<<<<<<<<
$.,$aprille                  , $lorem
   ^<<<<<<<<<<<<<<<<<<<<<<<< | ^<<<<<<<<<<<<<<<<<< ~~
   $aprille                  , $lorem
                             |
.

while(<DATA>) {
  ($aprille, $lorem) = split(/\|/, $_, 2);
  write;
}

__DATA__
WHAN that Aprille with his shoures soote       |Lorem ipsum dolor sit amet,
The droghte of Marche hath perced to the roote,|consectetur adipisicing elit,
And bathed every veyne in swich licour,        |sed do eiusmod tempor
Of which vertu engendred is the flour;         |incididunt ut labore et dolore
Whan Zephirus eek with his swete breeth        |magna aliqua. Ut enim ad minim
Inspired hath in every holt and heeth          |veniam, quis nostrud
The tendre croppes, and the yonge sonne        |exercitation exercitation
Hath in the Ram his halfe cours y-ronne,       |ullamco laboris nisi ut ali-
And smale fowles maken melodye,                |quip ex ea commodo conse-
That slepen al the night with open ye,         |quat. Duis aute irure dolor
So priketh hem nature in hir corages:          |in reprehenderit in volup-
Than longen folk to goon on pilgrimages,       |tate velit esse cillium dol-
And palmers for to seken straunge strondes,    |ore eu fugiat nulla pariatur.
To ferne halwes, couthe in sondry londes;      |Lorem ipsum dolor sit amet,
And specially, from every shires ende          |consectetur adipisicing elit,
Of Engelond, to Caunterbury they wende,        |sed do eiusmod tempor
The holy blisful martir for to seke,           |incididunt ut labore et dolore
That hem hath holpen, whan that they were seke.|magna aliqua. Ut enim ad minim
And now for something completely different. Nice plumage.|Norwegian blue.

Produces

   1 WHAN that Aprille with    | Lorem ipsum dolor
     his shoures soote         | sit amet,
                               |
   2 The droghte of Marche     | consectetur
     hath perced to the roote, | adipisicing elit,
                               |
   3 And bathed every veyne in | sed do eiusmod
     swich licour,             | tempor
  ...
  19 And now for something     | Norwegian blue.
     completely different.     |
     Nice plumage.             |

Note that record 19 occupies three lines.

What is an equivalent concise perl5ish way to do the above without using write and format?

Answer 1

The main problem with formats is the reliance on global variables. For other problems with formats, see pages 449 – 454 of Perl Best Practices.

The modern solution would be Perl6::Form. This is a backport of what they are planning for Perl 6.

What follows is a rough translation of your format code to Perl6::Form. I do not know Perl6::Form very well, so there may be ways to make it better or truer to your original example:

#!/usr/bin/perl

use strict;
use warnings;

use Perl6::Form;

while(<DATA>) {
    my ($aprille, $lorem) = split(/\|/, $_, 2);
    print form(
        "{>} {[[[[[[[[[[[[[[[[[[[[[[[[} | {[[[[[[[[[[[[[[[[[[}",
        $.,  $aprille,                  $lorem,
        "                               |                     ",
    );
}

__DATA__
WHAN that Aprille with his shoures soote       |Lorem ipsum dolor sit amet,
The droghte of Marche hath perced to the roote,|consectetur adipisicing elit,
And bathed every veyne in swich licour,        |sed do eiusmod tempor
Of which vertu engendred is the flour;         |incididunt ut labore et dolore
Whan Zephirus eek with his swete breeth        |magna aliqua. Ut enim ad minim
Inspired hath in every holt and heeth          |veniam, quis nostrud
The tendre croppes, and the yonge sonne        |exercitation exercitation
Hath in the Ram his halfe cours y-ronne,       |ullamco laboris nisi ut ali-
And smale fowles maken melodye,                |quip ex ea commodo conse-
That slepen al the night with open ye,         |quat. Duis aute irure dolor
So priketh hem nature in hir corages:          |in reprehenderit in volup-
Than longen folk to goon on pilgrimages,       |tate velit esse cillium dol-
And palmers for to seken straunge strondes,    |ore eu fugiat nulla pariatur.
To ferne halwes, couthe in sondry londes;      |Lorem ipsum dolor sit amet,
And specially, from every shires ende          |consectetur adipisicing elit,
Of Engelond, to Caunterbury they wende,        |sed do eiusmod tempor
The holy blisful martir for to seke,           |incididunt ut labore et dolore
That hem hath holpen, whan that they were seke.|magna aliqua. Ut enim ad minim
And now for something completely different. Nice plumage.|Norwegian blue.