How are lexical warnings supposed to work?

[p5pRT]

Migrated from rt.perl.org#909 (status was 'resolved')

Searchable as RT909$

[p5pRT]

From @jandubois

#================================
use warning;
{
  print "Oops\n" if $var == 1;
  print "Done\n";
}
#--------------------------------
perl unint.pl
Name "main​::var" used only once​: possible typo at uninit.pl line 4.
Use of uninitialized value at uninit.pl line 4.
Done
#================================

which is as expected. But​:

#================================
{
  use warning;
  print "Oops\n" if $var == 1;
  print "Done\n";
}
#--------------------------------
perl uninit.pl
Use of uninitialized value at uninit.pl line 4.
Done
#================================

Why did the "once" warning go away? And if I disable any warning​:

#================================
use warning;
{
  no warning qw(printf);
  print "Oops\n" if $var == 1;
  print "Done\n";
}
#--------------------------------
perl uninit.pl
Name "main​::var" used only once​: possible typo at uninit.pl line 5.
Done
#================================

The "uninitialized" message goes away (but shouldn't IMO). Am I missing
something or does it just not work yet reliably?

-Jan

perl -V
Summary of my perl5 (revision 5.0 version 5 subversion 57) configuration​:
  Platform​:
  osname=MSWin32, osvers=4.0, archname=MSWin32-x86
  uname=''
  config_args='undef'
  hint=recommended, useposix=true, d_sigaction=undef
  usethreads=undef useperlio=undef d_sfio=undef
  use64bits=undef usemultiplicity=undef
  Compiler​:
  cc='cl.exe', optimize='-O2 -MD -DNDEBUG', gccversion=
  cppflags='-DWIN32'
  ccflags ='-O2 -MD -DNDEBUG -DWIN32 -D_CONSOLE -DNO_STRICT '
  stdchar='char', d_stdstdio=define, usevfork=false
  intsize=4, longsize=4, ptrsize=4, doublesize=8
  d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=10
  alignbytes=8, usemymalloc=n, prototype=define
  Linker and Libraries​:
  ld='link', ldflags ='-nologo -nodefaultlib -release -machine​:x86'
  libpth=i​:\vs\vc98\lib
  libs= oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib
comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib netapi32.lib
uuid.lib wsock32.lib mpr.lib winmm.lib version.lib odbc32.lib
odbccp32.lib PerlCRT.lib
  libc=PerlCRT.lib, so=dll, useshrplib=yes, libperl=perl.lib
  Dynamic Linking​:
  dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
  cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -release
-machine​:x86'

Characteristics of this binary (from libperl)​:
  Locally applied patches​:
  g​:/incoming/perl/Patches/Change.3484
  g​:/incoming/perl/Patches/pwenttest.diff
  Built under MSWin32
  Compiled at May 29 1999 09​:58​:50
  @​INC​:
  i​:/tmp/perl/557-opt/lib/MSWin32-x86
  i​:/tmp/perl/557-opt/lib
  i​:/tmp/perl/site/557-opt/lib/MSWin32-x86
  i​:/tmp/perl/site/557-opt/lib
  .