The difference is more visible this way: 
use Devel::Peek;
Dump("");
Dump(!1);

[download]
The output of which is 
SV = PV(0x816d944) at 0x8163c48
  REFCNT = 1
  FLAGS = (PADBUSY,PADTMP,POK,READONLY,pPOK)
  PV = 0x8167830 ""\0
  CUR = 0
  LEN = 1
SV = PVNV(0x814d6a0) at 0x814c600
  REFCNT = 2147483647
  FLAGS = (PADBUSY,PADTMP,NOK,POK,READONLY,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x814d678 ""\0
  CUR = 0
  LEN = 1
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re^6: "last expression" quiz by japhy
in thread "last expression" quiz by fxn

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.