Rob, I have 5.20.1 with COW turned off. When recompiled with COW turned on, then it keeps the value, as you found. Below are the configure arguments that creates the error. Agree its an error? I turn COW off to avoid the problems discussed earlier, and will stay with the latest perl that allows turning COW off.
I am not generally constrained by perl, the few annoyances being: inability to reclaim memory, to uninstall a module and have warnings for all unused variables. And then COW and now this. Niels ------------------------------------------------ ~/BION/Software/bin> ./perl -V Summary of my perl5 (revision 5 version 20 subversion 1) configuration: Platform: osname=linux, osvers=3.13.0-24-generic, archname=i686-linux-64int uname='linux think2 3.13.0-24-generic #47-ubuntu smp fri may 2 23:31:42 utc 2014 i686 gnulinux ' config_args='-de -Accflags=-fPIC -Accflags=-DPERL_NO_COW -Dprefix=/home/niels/BION/Software/Package_installs/Perl -Duse64bitint' hint=recommended, useposix=true, d_sigaction=define useithreads=undef, usemultiplicity=undef use64bitint=define, use64bitall=undef, uselongdouble=undef usemymalloc=n, bincompat5005=undef Compiler: cc='cc', ccflags ='-fPIC -DPERL_NO_COW -fwrapv -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64', optimize='-O2', cppflags='-fPIC -DPERL_NO_COW -fwrapv -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include' ccversion='', gccversion='4.8.2', gccosandvers='' intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12 ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8 alignbytes=4, prototype=define Linker and Libraries: ld='cc', ldflags =' -fstack-protector -L/usr/local/lib' libpth=/home/niels/BION/Software/lib /usr/local/lib /usr/lib/gcc/i686-linux-gnu/4.8/include-fixed /usr/include/i386-linux-gnu /usr/lib /lib/i386-linux-gnu /lib/../lib /usr/lib/i386-linux-gnu /usr/lib/../lib /lib libs=-lnsl -ldl -lm -lcrypt -lutil -lc perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc libc=libc-2.19.so, so=so, useshrplib=false, libperl=libperl.a gnulibc_version='2.19' Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E' cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector' Characteristics of this binary (from libperl): Compile-time options: HAS_TIMES PERLIO_LAYERS PERL_DONT_CREATE_GVSV PERL_HASH_FUNC_ONE_AT_A_TIME_HARD PERL_MALLOC_WRAP PERL_PRESERVE_IVUV PERL_SAWAMPERSAND USE_64_BIT_INT USE_LARGE_FILES USE_LOCALE USE_LOCALE_COLLATE USE_LOCALE_CTYPE USE_LOCALE_NUMERIC USE_PERLIO USE_PERL_ATOF Built under linux Compiled at Sep 14 2014 20:40:59 @INC: /home/niels/BION/Software/Package_installs/Perl/lib/perl5/site_perl/5.20.1/i686-linux-64int /home/niels/BION/Software/Package_installs/Perl/lib/perl5/site_perl/5.20.1 /home/niels/BION/Software/Package_installs/Perl/lib/perl5/5.20.1/i686-linux-64int /home/niels/BION/Software/Package_installs/Perl/lib/perl5/5.20.1 . ~/BION/Software/bin> _______________________________________________ Perldl mailing list Perldl@jach.hawaii.edu http://mailman.jach.hawaii.edu/mailman/listinfo/perldl