Re^6: how do I "initialize" $

In an oversight since corrected, I neglected to mention that the code here was run under Perl version 5.8.9.

I tried

while (my $line = <DATA>)
{
   print $line;
}
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with my original __DATA__ both with and without a newline after the 0 on the final line and with strictures and warnings fully enabled and under 5.8.9 and saw no difference in behavior (and no warnings). The reason is easy to see from a deparse:

c:\@Work\Perl\monks\Marshall>perl -MO=Deparse,-p t_read_DATA_2.pl
use warnings;
use strict 'refs';
print("perl version: $] \n\n");
while (defined((my $line = <DATA>))) {
    do {
        print($line)
    };
}
__DATA__
line the first
second line
penultimate line is line 3
t_read_DATA_2.pl syntax OK
0
[download]

The defined test is automatically added.

Give a man a fish: <%-{-{-{-<

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Re^7: how do I "initialize" $_ by Marshall (Canon) on Oct 13, 2018 at 09:51 UTC
Interesting. In any event apparently defined() on the <DATA> file handle is not needed - or at least not any more. Update: I haven't been able to reproduce this warning on my current Perl 5.24 version. From what I remember the warning was unusually specific in what it said - this was very specific. To my knowledge, I never did actually try Perl code that would cause the problem that was warned about. This was a warning about something that could potentially happen - not an error. This situation did not occur in my source code. I just took Perl at "its word" and adjusted my source code so that this warning went away. I think of Perl as a living, breathing, biological organism that evolves over time. It is completely possible that this was an extraneous warning about something that didn't really matter. At this point, I don't know. It could be that this warning was just emitted in one version of Perl and corrected in the next version. I've worked with a lot of versions of Perl. I don't have nor would I have saved the exact text of this warning.	[reply]

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Re^7: how do I "initialize" $_
by Marshall (Canon) on Oct 13, 2018 at 09:51 UTC

In any event apparently defined() on the <DATA> file handle is not needed - or at least not any more.

Update: I haven't been able to reproduce this warning on my current Perl 5.24 version. From what I remember the warning was unusually specific in what it said - this was very specific. To my knowledge, I never did actually try Perl code that would cause the problem that was warned about. This was a warning about something that could potentially happen - not an error. This situation did not occur in my source code. I just took Perl at "its word" and adjusted my source code so that this warning went away.

I think of Perl as a living, breathing, biological organism that evolves over time. It is completely possible that this was an extraneous warning about something that didn't really matter. At this point, I don't know. It could be that this warning was just emitted in one version of Perl and corrected in the next version. I've worked with a lot of versions of Perl. I don't have nor would I have saved the exact text of this warning.

[reply]