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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);
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?


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

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