[perl #134156] use feature ':all'

# New Ticket Created by  Diab Jerius 
# Please include the string:  [perl #134156]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=134156 >



This is a bug report for perl from djerius@cpan.org,
generated with the help of perlbug 1.41 running under perl 5.28.1.


-----------------------------------------------------------------
[Please describe your issue here]

As of Perl v5.16, the feature pragma has provided an import tag of :all.

The documentation describes its use only in the negative, e.g. when explaining
how 

  use v5.10.0;

works via

  no feature ':all';
  use feature ':5.10';

Is there a reason that one should not use ':all' positively? As in

  use feature ':all';

Today a Perl beginner posted on stackoverflow [1] about the
mysterious errors they were getting when they removed the 'use 5.30'
from their program.  Many of the responses revolved around what a
feature was, and how to enable particular features, and which version a
feature was found in.

While the beginner's dilemma opened up a pedagogical opportunity, it
struck me that it also dramatically increased the cognitive load for a
newcomer, as it forces them to delve into the minutiae of features.

There's a handy CPAN module, 'latest', which gives the program access
to the latest features available on the running Perl. The ':all' tag
accomplishes the same thing, with the benefit that it is a standard
part of the more recent modern Perls.


If there are no objections to using ':all' to import symbols, it would
make sense to indicate that in the documentation; one could simply
then suggest to the beginner to

  use feature ':all';

to get their code working, and point them at the feature pragma for
future exploration.

Thanks as always for your efforts!

Diab



[1] https://stackoverflow.com/questions/56399608/helloworld-example-for-perl-gives-two-errors-when-not-specifying-use-5-30-0

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=library
    severity=wishlist
    module=feature
---
Site configuration information for perl 5.28.1:

Configured by dj at Mon Dec 17 10:30:49 EST 2018.

Summary of my perl5 (revision 5 version 28 subversion 1) configuration:
   
  Platform:
    osname=linux
    osvers=4.9.0-8-amd64
    archname=x86_64-linux_debian-9-thread-multi
    uname='linux macabre 4.9.0-8-amd64 #1 smp debian 4.9.110-3+deb9u5 (2018-09-30) x86_64 gnulinux '
    config_args='-de -Dprefix=/proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9 -Uinstallusrbinperl -Dperladmin=none -Dlocincpth=/proj/axaf/ots/include -Darchname=x86_64-linux_debian-9 -Dusethreads -Dotherlibdirs=/proj/axaf/simul/lib/perl5:/proj/axaf/simul/x86_64-linux_debian-9/lib/perl5 -Dloclibpth=/proj/axaf/ots/x86_64-linux_debian-9/lib -Dglibpth=/lib /usr/lib -Dldflags=-L/proj/axaf/ots/x86_64-linux_debian-9/lib -Wl,-rpath=/proj/axaf/ots/x86_64-linux_debian-9/lib -Duseshrplib'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='cc'
    ccflags ='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/proj/axaf/ots/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O2'
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/proj/axaf/ots/include'
    ccversion=''
    gccversion='6.3.0 20170516'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='cc'
    ldflags ='-L/proj/axaf/ots/x86_64-linux_debian-9/lib -Wl,-rpath=/proj/axaf/ots/x86_64-linux_debian-9/lib -fstack-protector-strong'
    libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/6/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /proj/axaf/ots/x86_64-linux_debian-9/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
    libs=-lpthread -lnsl -lgdbm -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.24.so
    so=so
    useshrplib=true
    libperl=libperl.so
    gnulibc_version='2.24'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E -Wl,-rpath,/proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/5.28.1/x86_64-linux_debian-9-thread-multi/CORE'
    cccdlflags='-fPIC'
    lddlflags='-shared -O2 -L/proj/axaf/ots/x86_64-linux_debian-9/lib -fstack-protector-strong'


---
@INC for perl 5.28.1:
    /proj/axaf/simul/lib/perl5/x86_64-linux_debian-9-thread-multi
    /proj/axaf/simul/lib/perl5
    /home/dj/research/lib/perl5
    /proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/site_perl/5.28.1/x86_64-linux_debian-9-thread-multi
    /proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/site_perl/5.28.1
    /proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/5.28.1/x86_64-linux_debian-9-thread-multi
    /proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/5.28.1
    /proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/site_perl/5.28.0/x86_64-linux_debian-9-thread-multi
    /proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/site_perl/5.28.0
    /proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/lib/site_perl
    /proj/axaf/simul/lib/perl5/x86_64-linux_debian-9-thread-multi
    /proj/axaf/simul/lib/perl5
    /proj/axaf/simul/x86_64-linux_debian-9/lib/perl5

---
Environment for perl 5.28.1:
    HOME=/home/dj
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH=/soft/SYBASE15.7/DataAccess64/ODBC/lib:/soft/SYBASE15.7/DataAccess/ODBC/lib:/soft/SYBASE15.7/OCS-15_0/lib:/soft/SYBASE15.7/OCS-15_0/lib3p64:/soft/SYBASE15.7/OCS-15_0/lib3p:
    LOGDIR (unset)
    PATH=/home/dj/.plenv/libexec:/home/dj/.plenv/plugins/link-axaf/bin:/home/dj/.plenv/plugins/perl-build/bin:/home/dj/.plenv/plugins/plenv-contrib/bin:/soft/SYBASE15.7/OCS-15_0/bin:/home/dj/.rbenv/shims:/home/dj/.rbenv/bin:/home/dj/.pyenv/plugins/pyenv-virtualenv/shims:/home/dj/.pyenv/shims:/home/dj/.pyenv/bin:/home/dj/.plenv/shims:/home/dj/.plenv/bin:/home/dj/root/bin:/home/dj/root/bin/hosts:/home/dj/research/bin:/proj/axaf/ots/pkgs/perl-5.28/x86_64-linux_debian-9/bin:/proj/axaf/bin:/proj/axaf/simul/bin:/proj/axaf/simul/x86_64-linux_debian-9/bin:/proj/axaf/ots/x86_64-linux_debian-9/bin:/proj/axaf/ots/bin:/usr/local/bin:/usr/sbin:/bin:/usr/bin:/soft/saord/bin
    PERL5LIB=/proj/axaf/simul/lib/perl5:/home/dj/research/lib/perl5
    PERL_BADLANG (unset)
    PERL_CPANM_HOME=/tmp/dj/cpanm
    PERL_CPANM_OPT=--cascade --mirror /proj/axaf/simul/export/darkpan --mirror https://cpan.org
    SHELL=/bin/bash

• [perl #134156] use feature ':all' by Diab Jerius
• Re: [perl #134156] use feature ':all' by Dave Mitchell
• Re: [perl #134156] use feature ':all' by Diab Jerius