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  1. use warnings;
  2. use strict;
  3. use feature ':5.10';
  4.  
  5. use B;
  6.  
  7. # Type and flags for reference
  8. my $obj = B::svref_2object(\(my $dummy = !!1));
  9. my $TYPE = $obj->SvTYPE;
  10. my $FLAGS = $obj->FLAGS;
  11.  
  12. sub looks_like_bool {
  13.   my $bool = shift;
  14.  
  15.   # Compare type
  16.   my $obj = B::svref_2object(\$bool);
  17.   return !!0 unless $obj->SvTYPE == $TYPE;
  18.  
  19.   # Compare flags
  20.   return !!0 unless $obj->FLAGS == $FLAGS;
  21.  
  22.   # True value
  23.   return !!1 if $bool eq !!1;
  24.  
  25.   # False value
  26.   return !!1 if $bool eq !!0;
  27.  
  28.   # Not a boolean
  29.   return !!0;
  30. }
  31.  
  32. print "----boolean----\n";
  33. for (
  34.   {say => 'Boolean true', var => !!1},
  35.   {say => 'Boolean false', var => !!0}
  36.  ) {
  37.   say $_->{say} if looks_like_bool $_->{var};
  38. }
  39. print "----non-boolean----\n";
  40. for (
  41.   {say => 'Random string', var => 'whatever'},
  42.   {say => 'Random integer', var =>  23},
  43.   {say => 'Random float', var =>  23.23},
  44.   {say => 'Fake false', var =>  0e0},
  45.   {say => '0 but true', var => '0 but true'},
  46.   {say => 'An arrayref',  var => []},
  47.  ) {
  48.   say $_->{say} unless looks_like_bool $_->{var};
  49. }
Success #stdin #stdout 0.01s 5056KB
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----boolean----
Boolean true
Boolean false
----non-boolean----
Random string
Random integer
Random float
Fake false
0 but true
An arrayref
https://ideone.com/2FSn0O
language:
Perl (perl 5.28.1)
created:
11 years ago
visibility:
public

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