Why do my Perl tests fail with use encoding 'utf8'?

Question

I'm puzzled with this test script:

#!perl

use strict;
use warnings;
use encoding 'utf8';
use Test::More 'no_plan';

ok('áá' =~ m/á/, 'ok direct match');

my $re = qr{á};
ok('áá' =~ m/$re/, 'ok qr-based match');

like('áá', $re, 'like qr-based match');

The three tests fail, but I was expecting that the use encoding 'utf8' would upgrade both the literal áá and the qr-based regexps to utf8 strings, and thus passing the tests.

If I remove the use encoding line the tests pass as expected, but I can't figure it out why would they fail in utf8 mode.

I'm using perl 5.8.8 on Mac OS X (system version).

Answer 1

Do not use the encoding pragma. It’s broken. (Juerd Waalboer gave a great talk where he mentioned this at YAPC::EU 2k8.)

It does at least two things at once that do not belong together:

1. It specifies an encoding for your source file.
2. It specifies an encoding for your file input/output.

And to add injury to insult it also does #1 in a broken fashion: it reinterprets \xNN sequences as being undecoded octets as opposed to treating them like codepoints, and decodes them, preventing you from being able to express characters outside the encoding you specified and making your source code mean different things depending on the encoding. That’s just astonishingly wrong.

Write your source code in ASCII or UTF-8 only. In the latter case, the utf8 pragma is the correct thing to use. If you don’t want to use UTF-8, but you do want to include non-ASCII charcters, escape or decode them explicitly.

And use I/O layers explicitly or set them using the open pragma to have I/O automatically transcoded properly.