note
ikegami
<blockquote><p><i>Also, it isn't necessary for $_ to be undefined (or unassigned) for the loop to end. </i></blockquote>
<p>While that's true in general,
<c>
>perl -le"$_=4; while (--$_) { print }"
3
2
1
</c>
<p>It's not true in this case.
<c>
>perl -e"print 0" | perl -le"while ($_ = <>) { print $_ ? 'true' : 'false' }"
false
>perl -MO=Deparse -e"while (<>) {}"
while (defined($_ = <ARGV>)) {
();
}
-e syntax OK
>perl -MO=Deparse -e"while ($_ = <>) {}"
while (defined($_ = <ARGV>)) {
();
}
-e syntax OK
>perl -MO=Deparse -e"while (defined($_ = <>)) {}"
while (defined($_ = <ARGV>)) {
();
}
-e syntax OK
</c>
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