Meta Interchange

I noticed that a patch recently submitted for Koha adds the following line to one of Koha’s Perl modules:

use utf8;

utf8 is a perfectly fine and proper Perl pragma, right? Indeed it is. The problem is that the purpose of the patch is to try to fix an issue with reading and displaying UTF-8 characters from a file. So what does use utf8; contribute to that patch?

Nothing.

The only thing that the utf8 pragma does is signal to the Perl interpreter that the Perl source code is in UTF-8. If you’re using non-ASCII characters in your source code, you’ll need the pragma. For example,

use utf8;
my $str = "La lluvia en España se mantiene principalmente en el llano!";

or even

use utf8;
my $str_en_inglés = "The rain in Spain falls mostly on the plain!";

If what you’re actually trying to do is ensure that the script is handling UTF-8 input and output correctly, use utf8; won’t help. This tutorial will.

Not paying close attention to Perl’s definition of truth can sometimes lead to subtle bugs. Consider a simple scalar $x that should contain a string exactly one character wide. If the original value of $x can be undefined and you want to make sure it has a default value of a single space, do not do the following:

$x ||= ' ';


Why not? If $x starts off as ’0′, a permitted value, this line will change it to ' '. Instead, do this

$x = ' ' unless defined $x;


Remember, 0, '0', '', and undef all evaluate to Perl’s notion of false.