I give up. I cannot tell dualvar 0,"0 " from "0 ": 
use Devel::Peek;
use Scalar::Util qw/dualvar/;

my @x = ("0 ",dualvar(0,"0 "));
(10.2+$_).$_ for @x;
Dump $x[0];
Dump $x[1];

[download]
gives 
SV = PVNV(0x830ef78) at 0x8310564
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x835465c "0 "\0
  CUR = 2
  LEN = 4
SV = PVNV(0x830ef8c) at 0x8310584
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x833b77c "0 "\0
  CUR = 2
  LEN = 4

[download]

In reply to Re^3: Determining whether a value is zero. by choroba
in thread Determining whether a value is zero. by JavaFan

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