indeed :) 
#!/usr/bin/perl --
use Devel::Peek qw/ Dump /;
select STDERR;
print "\n\$ARGV\n";                  Dump( $ARGV );
print "\nundef\n";                   Dump( undef );
print "\n!!0 PL_sv_no\n";            Dump( !!0 );
print "\ndefined undef\n";           Dump( defined undef );
print "\n!!1 PL_sv_yes\n";           Dump( !!1 );
print "\ndefined defined undef\n";   Dump( defined defined undef );
__END__

[download]

$ARGV
SV = NULL(0x0) at 0x99b90c
  REFCNT = 1
  FLAGS = ()

undef
SV = NULL(0x0) at 0x3f4cc0
  REFCNT = 2147482895
  FLAGS = (READONLY)

!!0 PL_sv_no
SV = PVNV(0x3f7f84) at 0x3f4968
  REFCNT = 2147483646
  FLAGS = (PADTMP,IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x3f405c ""\0
  CUR = 0
  LEN = 12

defined undef
SV = PVNV(0x3f7f84) at 0x3f4968
  REFCNT = 2147483646
  FLAGS = (PADTMP,IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x3f405c ""\0
  CUR = 0
  LEN = 12

!!1 PL_sv_yes
SV = PVNV(0x3f7f9c) at 0x3f4978
  REFCNT = 2147483643
  FLAGS = (PADTMP,IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x3f8e7c "1"\0
  CUR = 1
  LEN = 12

defined defined undef
SV = PVNV(0x3f7f9c) at 0x3f4978
  REFCNT = 2147483643
  FLAGS = (PADTMP,IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x3f8e7c "1"\0
  CUR = 1
  LEN = 12

In reply to Re^4: defined defined -- Bug or "Feature"? by Anonymous Monk
in thread defined defined -- Bug or "Feature"? by roho

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.