Sometimes while(...) magically deparsed to while(defined(...)), but sometimes it doesn't. How is this decision made? 
#### GLOBS cause defined to show up
  # while(<*.pl>) {}         DEFINEDNESS
  % perl -MO=Deparse -e 'while(<*.pl>) {}'
  while (defined($_ = CORE::GLOBAL::glob('*.pl', 0))) {
      ();
  }

  # 1 while (<*.pl>)         DEFINEDNESS
  % perl -MO=Deparse -e '1 while(<*.pl>)'
  '???' while defined($_ = CORE::GLOBAL::glob('*.pl', 0));

#### Simple vars dont
  # while($x) {}             TRUTHFULNESS
  % perl -MO=Deparse -e 'while($x) {}'
  while ($x) {
      (); 
  }
  # '1 while($x)'            TRUTHFULNESS
  % perl -MO=Deparse -e '1 while($x)'
  '???' while $x;

#### Why do these two behave differently????
  # 'while($x = <*.pl>) {}   DEFINEDNESS
  % perl -MO=Deparse -e 'while($x = <*.pl>) {}'
  while (defined($x = CORE::GLOBAL::glob('*.pl', 0))) {
      ();
  }

  # '1 while($x = <*.pl>)    TRUTHFULNESS
  % perl -MO=Deparse -e '1 while($x = <*.pl>)'
  '???' while $x = CORE::GLOBAL::glob('*.pl', 0);

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I looked for documentation on this behaviour but couldn't find any. Flow control keywords aren't listed in perlfunc, do they have their own perldoc page?

-Blake

In reply to When does while() test for defined vs truth by blakem

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