Also, it isn't necessary for $_ to be undefined (or unassigned) for the loop to end.

While that's true in general, 

>perl -le"$_=4; while (--$_) { print }"
3
2
1

[download]

It's not true in this case. 

>perl -e"print 0" | perl -le"while ($_ = <>) { print $_ ? 'true' : 'fa
+lse' }"
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

[download]

In reply to Re^2: "defined" in while loop Edit | Delete | Quote | Reply | Private Reply by ikegami
in thread "defined" in while loop Edit | Delete | Quote | Reply | Private Reply by manish.rathi

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