looks_like_bool.pl

use warnings;
use strict;
use feature ':5.10';

use B;

# Type and flags for reference
my $obj = B::svref_2object(\(my $dummy = !!1));
my $TYPE  = $obj->SvTYPE;
my $FLAGS = $obj->FLAGS;

sub looks_like_bool {
  my $bool = shift;

  # Compare type
  my $obj = B::svref_2object(\$bool);
  return !!0 unless $obj->SvTYPE == $TYPE;

  # Compare flags
  return !!0 unless $obj->FLAGS == $FLAGS;

  # True value
  return !!1 if $bool eq !!1;

  # False value
  return !!1 if $bool eq !!0;

  # Not a boolean
  return !!0;
}

say 'Boolean true' if looks_like_bool !!1;
my $true = !!1;
say 'Boolean true'  if looks_like_bool $true;
say 'Boolean false' if looks_like_bool !!0;
my $false = !!0;
say 'Boolean false' if looks_like_bool $false;
say 'Random string'  unless looks_like_bool 'whatever';
say 'Zero'           unless looks_like_bool 0;
say 'One'            unless looks_like_bool 1;
say 'Random integer' unless looks_like_bool 23;
say 'Random float'   unless looks_like_bool 23.23;

While this does detect what perl internals returns as booleans, there is nothing special about them.

my $y = 11.5 - 10.5;
my $tmp = 1+$y;
$tmp = "$y";

say "Generated Boolean" if looks_like_bool($y);

@gbarr You sunk my battleship.

<3 @gbarr