The default scalar  $_ (see perlvar) is assigned to in some cases, but not all; you've chosen one of the "not all" cases. A while-loop like 

while (<FILEHANDLE>) {
    print;
    }

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is really 
while (defined($_ = <FILEHANDLE>)) {
    print $_;
    }

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and likewise 
for (<FILEHANDLE>) {
    print;
    }

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is 
for $_ (<FILEHANDLE>) {
    print $_;
    }

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(Note that the while-loop will read and print the filehandle line-by-line, but the for-loop will read all lines of the file at once (could be a lotta lines!) and then print the lines one-by-one.) See perlsyn.

Give a man a fish:  <%-{-{-{-<

In reply to Re: how do I "initialize" $_ by AnomalousMonk
in thread how do I "initialize" $_ by Anonymous Monk

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