I forgot to mention that your loop will not execute if a line evaluating to false in boolean context is read

Actually, no - if you read the perlop 'I/O Operators' entry carefully, you'll find that using <FILEHANDLE> inside a while (or for(;;)) construct is treated specially - a defined test is done for you, to avoid exactly the problem you mention...

I case you're too lazy to look it up, I quote:

In these loop constructs, the assigned value (whether assignment is automatic or explicit) is then tested to see whether it is defined. The defined test avoids problems where line has a string value that would be treated as false by Perl, for example a "" or a "0" with no trailing newline. If you really mean for such values to terminate the loop, they should be tested for explicitly:

           while (($_ = <STDIN>) ne '0') { ... }
           while (<STDIN>) { last unless $_; ... }
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In other boolean contexts, "<filehandle>" without an explicit "defined" test or comparison elicit a warning if the "use warnings" pragma or the -w command-line switch (the "$^W" variable) is in effect.

HTH

You're right; I just confirmed this with B::Deparse. Thanks!

$ perl -MO=Deparse
while (my $in = <STDIN>)
{
    print $in;
}
^D
while (defined(my $in = <STDIN>)) {
    print $in;
}
- syntax OK
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