#!/usr/bin/perl -l
use strict;
use warnings;
use Devel::Peek;

sub display {
    my $text = shift;
    my $result = shift;
    my $ans = ($result) ? 'TRUE' : 'FALSE';
    print STDERR "$text => CONDITIONAL WAS $ans";
    Dump $result;
    print STDERR '-'x20, "\n";
}

my @results;
push @results, ['1==1', 1==1];
push @results, ['defined("x")', defined 'x'];
push @results, ['defined("x")==1', defined('x')==1];
push @results, ['defined("x")eq"1"', defined('x')eq"1"];
push @results, ['1==0', 1==0];
push @results, ['defined(undef)', defined undef];
push @results, ['!defined(undef)', !defined undef];
push @results, ['defined(undef)==0', defined(undef)==0];
push @results, ['defined(undef)eq""', defined(undef)eq""];
display(@$_) for ( @results );

__END__
1==1 => CONDITIONAL WAS TRUE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x47c3e8 "1"\0
  CUR = 1
  LEN = 10
--------------------

defined("x") => CONDITIONAL WAS TRUE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x47c3e8 "1"\0
  CUR = 1
  LEN = 10
--------------------

defined("x")==1 => CONDITIONAL WAS TRUE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x47c3e8 "1"\0
  CUR = 1
  LEN = 10
--------------------

defined("x")eq"1" => CONDITIONAL WAS TRUE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x47c3e8 "1"\0
  CUR = 1
  LEN = 10
--------------------

1==0 => CONDITIONAL WAS FALSE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x47c3e8 ""\0
  CUR = 0
  LEN = 10
--------------------

defined(undef) => CONDITIONAL WAS FALSE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x47c3e8 ""\0
  CUR = 0
  LEN = 10
--------------------

!defined(undef) => CONDITIONAL WAS TRUE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x47c3e8 "1"\0
  CUR = 1
  LEN = 10
--------------------

defined(undef)==0 => CONDITIONAL WAS TRUE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x47c3e8 "1"\0
  CUR = 1
  LEN = 10
--------------------

defined(undef)eq"" => CONDITIONAL WAS TRUE
SV = PVNV(0x5de5c8) at 0x479ab8
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x47c3e8 "1"\0
  CUR = 1
  LEN = 10
--------------------