strange behaviour with 'use open IN => ":byte"

[loopology]

If I run this script:

#!/usr/bin/perl
use open IN => ":byte";
use constant A => 1;

on a MacBook Pro (Intel)

With perl version 5.8.6 (the pre-installed)

I get this error:
Can't locate constant.pm in @INC (@INC contains: /sw/lib/perl5 /sw/lib/
perl5/dar
win /System/Library/Perl/5.8.6/darwin-thread-multi-2level /System/
Library/Perl/5
..8.6 /Library/Perl/5.8.6/darwin-thread-multi-2level /Library/Perl/
5.8.6 /Library
/Perl /Network/Library/Perl/5.8.6/darwin-thread-multi-2level /Network/
Library/Pe
rl/5.8.6 /Network/Library/Perl /System/Library/Perl/Extras/5.8.6/
darwin-thread-m
ulti-2level /System/Library/Perl/Extras/5.8.6 /Library/Perl/5.8.1 .)
at ./tst.pl
line 3.

if I change the line to:
use open IN => ":encoding(UTF16-BE)";
I get this error:
Unrecognized character \xE0 at /System/Library/Perl/5.8.6/constant.pm
line 1.

In both cases:
If I swap the lines, everything runs smoothly.

Anyone seen this behaviour?
What to do about it?

Thanks
Bernhard

Summary of my perl5 (revision 5 version 8 subversion 6) configuration:
Platform:
osname=darwin, osvers=8.0, archname=darwin-thread-multi-2level
uname='darwin b19.apple.com 8.0 darwin kernel version 8.3.0: mon
oct 3 20:04
:04 pdt 2005; root:xnu-792.6.22.obj~2release_ppc power macintosh
powerpc '
config_args='-ds -e -Dprefix=/usr -Dccflags=-g -pipe -Dldflags=-
Dman3ext=3
pm -Duseithreads -Duseshrplib'
hint=recommended, useposix=true, d_sigaction=define
usethreads=define use5005threads=undef useithreads=define
usemultiplicity=de
fine
useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
use64bitint=undef use64bitall=undef uselongdouble=undef
usemymalloc=n, bincompat5005=undef
Compiler:
cc='cc', ccflags ='-g -pipe -fno-common -DPERL_DARWIN -no-cpp-
precomp -fno-s
trict-aliasing -I/usr/local/include',
optimize='-O3',
cppflags='-no-cpp-precomp -g -pipe -fno-common -DPERL_DARWIN -no-
cpp-precomp
-fno-strict-aliasing -I/usr/local/include'
ccversion='', gccversion='4.0.1 (Apple Computer, Inc. build
5363)', gccosand
vers=''
intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
d_longlong=define, longlongsize=8, d_longdbl=define,
longdblsize=16

ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize
=8
alignbytes=8, prototype=define
Linker and Libraries:
ld='env MACOSX_DEPLOYMENT_TARGET=10.3 cc', ldflags ='-L/usr/local/
lib'
libpth=/usr/local/lib /usr/lib
libs=-ldbm -ldl -lm -lc
perllibs=-ldl -lm -lc
libc=/usr/lib/libc.dylib, so=dylib, useshrplib=true,
libperl=libperl.dylib
gnulibc_version=''
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
cccdlflags=' ', lddlflags='-bundle -undefined dynamic_lookup -L/
usr/local/li
b'


Characteristics of this binary (from libperl):
Compile-time options: MULTIPLICITY USE_ITHREADS USE_LARGE_FILES
PERL_IMPLICIT_
CONTEXT
Locally applied patches:
23953 - fix for File:ath::rmtree CAN-2004-0452 security
issue
33990 - fix for setuid perl security issues
SPRINTF0 - fixes for sprintf formatting issues - CVE-2005-3962
Built under darwin
Compiled at Nov 1 2006 17:07:31
%ENV:
PERL5LIB="/sw/lib/perl5:/sw/lib/perl5/darwin"
@INC:
/sw/lib/perl5
/sw/lib/perl5/darwin
/System/Library/Perl/5.8.6/darwin-thread-multi-2level
/System/Library/Perl/5.8.6
/Library/Perl/5.8.6/darwin-thread-multi-2level
/Library/Perl/5.8.6
/Library/Perl
/Network/Library/Perl/5.8.6/darwin-thread-multi-2level
/Network/Library/Perl/5.8.6
/Network/Library/Perl
/System/Library/Perl/Extras/5.8.6/darwin-thread-multi-2level
/System/Library/Perl/Extras/5.8.6
/Library/Perl/5.8.1

 

[Mumia W.]

If I run this script:

#!/usr/bin/perl
use open IN => ":byte";
use constant A => 1;

on a MacBook Pro (Intel)

With perl version 5.8.6 (the pre-installed)

I get this error:
Can't locate constant.pm in @INC (@INC contains: /sw/lib/perl5 /sw/lib/
perl5/dar
win /System/Library/Perl/5.8.6/darwin-thread-multi-2level /System/
Library/Perl/5
..8.6 /Library/Perl/5.8.6/darwin-thread-multi-2level /Library/Perl/
5.8.6 /Library
/Perl /Network/Library/Perl/5.8.6/darwin-thread-multi-2level /Network/
Library/Pe
rl/5.8.6 /Network/Library/Perl /System/Library/Perl/Extras/5.8.6/
darwin-thread-m
ulti-2level /System/Library/Perl/Extras/5.8.6 /Library/Perl/5.8.1 .)
at ./tst.pl
line 3.

if I change the line to:
use open IN => ":encoding(UTF16-BE)";
I get this error:
Unrecognized character \xE0 at /System/Library/Perl/5.8.6/constant.pm
line 1.

In both cases:
If I swap the lines, everything runs smoothly.

Anyone seen this behaviour?
What to do about it?
[...]

I'm able to reproduce this behavior on Debian Linux with Perl 5.8.4 and
Perl 5.9.4.

Note, ":byte" is not correct. The correct layer is ":bytes"; however,
Perl's reaction to the incorrect layer doesn't produce much clarity for
the programmer.

 

[Ben Morrow]

I'm able to reproduce this behavior on Debian Linux with Perl 5.8.4 and
Perl 5.9.4.

Note, ":byte" is not correct. The correct layer is ":bytes"; however,
Perl's reaction to the incorrect layer doesn't produce much clarity for
the programmer.

In any case, it seems that you should not 'use open' before you use any
other modules: in no case will applying custom PerlIO layers to the
module files produce the correct result. This should probably be
documented in L<open>...

OP: it's probably worth either dropping open altogether, or switching to
an INIT block instead of a BEGIN by replacing

use open IN => ':bytes';

with

INIT {
require open;
open->import(IN => ':bytes');
}

This in then occur later than any 'use' statements (except those in
string evals); note that you will still have to be careful of 'require'
statements executed at runtime.

This could perhaps be considered a bug in Perl: 'require' (or at least
'require MODULE' rather than 'require "FILE"') should probably *not*
honour the default PerlIO layers set by open. This may or may not be
fixable, due to backwards-compatibility...

Ben