>perl -e"print 0" | perl -le"while ($_ = <>) { print $_ ? 'true' : 'false' }" false >perl -MO=Deparse -e"while (<>) {}" while (defined($_ = )) { (); } -e syntax OK >perl -MO=Deparse -e"while ($_ = <>) {}" while (defined($_ = )) { (); } -e syntax OK >perl -MO=Deparse -e"while (defined($_ = <>)) {}" while (defined($_ = )) { (); } -e syntax OK