[perl #114504] $ENV{foo}=undef

# New Ticket Created by  Father Chrysostomos 
# Please include the string:  [perl #114504]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=114504 >


perldelta for 5.17.3 has this under Incompatible Changes:

=head2 C<$ENV{foo}=undef> deletes value from environ, like C<delete $ENV{foo}>

This facilitates use of C<local()> with C<%ENV> entries.  In previous versions
of Perl, C<undef> was converted to the empty string.


I don’t recall seeing this discussed.  This change makes Perl less consistent with itself.  For undef to be converted to the empty string is normal.  For $hash{key} = undef to delete the hash element is abnormal.  And I don’t see what it provides, except inconsistency.  We already have delete local.

I think this should be reverted.

---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.17.3:

Configured by sprout at Mon Jul 30 23:46:13 PDT 2012.

Summary of my perl5 (revision 5 version 17 subversion 3) configuration:
  Snapshot of: 7e2a0d4586762cf28c9cdfb3c49d57d805879ac9
  Platform:
    osname=darwin, osvers=10.5.0, archname=darwin-2level
    uname='darwin pint.local 10.5.0 darwin kernel version 10.5.0: fri nov 5 23:20:39 pdt 2010; root:xnu-1504.9.17~1release_i386 i386 '
    config_args='-de -Dusedevel -DDEBUGGING=-g'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-common -DPERL_DARWIN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
    optimize='-O3 -g',
    cppflags='-fno-common -DPERL_DARWIN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.2.1 (Apple Inc. build 5664)', gccosandvers=''
    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 =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib
    libs=-ldbm -ldl -lm -lutil -lc
    perllibs=-ldl -lm -lutil -lc
    libc=, so=dylib, useshrplib=false, libperl=libperl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags=' -bundle -undefined dynamic_lookup -L/usr/local/lib -fstack-protector'

Locally applied patches:
    

---
@INC for perl 5.17.3:
    /usr/local/lib/perl5/site_perl/5.17.3/darwin-2level
    /usr/local/lib/perl5/site_perl/5.17.3
    /usr/local/lib/perl5/5.17.3/darwin-2level
    /usr/local/lib/perl5/5.17.3
    /usr/local/lib/perl5/site_perl
    .

---
Environment for perl 5.17.3:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/sprout
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/usr/local/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [perl #114504] $ENV{foo}=undef by Father Chrysostomos
• Re: [perl #114504] $ENV{foo}=undef by Jesse Luehrs
• Re: [perl #114504] $ENV{foo}=undef by Eirik Berg Hanssen
• [perl #114504] $ENV{foo}=undef by Father Chrysostomos via RT
• Re: [perl #114504] $ENV{foo}=undef by Ricardo Signes
• Re: [perl #114504] $ENV{foo}=undef by Rev. Chip