Thanks to all for the excellent information.
Phil
On Wed, May 2, 2012 at 2:41 PM, $Bill Luebkert <dbec...@roadrunner.com> wrote:
> On 05/02/2012 06:56, Phillip Richcreek wrote:
>>
>> A recent post used a nice feature for providing test data to a script.
>> (See __DATA__ below) I've seen it before but never understood it. How
>> does it work? What signals the end of the data to the while (my $line
>> =<DATA>) { ? Is this a type of here document? Can someone point me
>> where it's descibed in the perl doc?
>
>
> perldata man page:
>
> Special Literals
> The special literals __FILE__, __LINE__, and __PACKAGE__ represent the
> current filename, line number, and package name at that point in your
> program. They may be used only as separate tokens; they will not be
> interpolated into strings. If there is no current package (due to an
> empty
> "package;" directive), __PACKAGE__ is the undefined value.
>
> The two control characters ^D and ^Z, and the tokens __END__ and __DATA__
> may be used to indicate the logical end of the script before the actual
> end
> of file. Any following text is ignored.
>
> Text after __DATA__ may be read via the filehandle "PACKNAME::DATA",
> where
> "PACKNAME" is the package that was current when the __DATA__ token was
> encountered. The filehandle is left open pointing to the contents after
> __DATA__. It is the program's responsibility to "close DATA" when it is
> done
> reading from it. For compatibility with older scripts written before
> __DATA__ was introduced, __END__ behaves like __DATA__ in the top level
> script (but not in files loaded with "require" or "do") and leaves the
> remaining contents of the file accessible via "main::DATA".
>
> See SelfLoader for more description of __DATA__, and an example of its
> use.
> Note that you cannot read from the DATA filehandle in a BEGIN block: the
> BEGIN block is executed as soon as it is seen (during compilation), at
> which
> point the corresponding __DATA__ (or __END__) token has not yet been
> seen.
>
> perlpod man page:
>
> Embedding Pods in Perl Modules
> You can embed Pod documentation in your Perl modules and scripts. Start
> your
> documentation with an empty line, a "=head1" command at the beginning,
> and
> end it with a "=cut" command and an empty line. Perl will ignore the Pod
> text. See any of the supplied library modules for examples. If you're
> going
> to put your Pod at the end of the file, and you're using an __END__ or
> __DATA__ cut mark, make sure to put an empty line there before the first
> Pod
> command.
>
> __END__
>
> =head1 NAME
>
> perl561delta man page:
>
> Scripts are read in binary mode by default to allow ByteLoader (and the
> filter mechanism in general) to work properly. For compatibility, the
> DATA
> filehandle will be set to text mode if a carriage return is detected at
> the
> end of the line containing the __END__ or __DATA__ token; if not, the
> DATA
> filehandle will be left open in binary mode. Earlier versions always
> opened
> the DATA filehandle in text mode.
> ...
>
> Potential to leak DATA filehandles
> Using the "__DATA__" token creates an implicit filehandle to the file
> that
> contains the token. It is the program's responsibility to close it when
> it
> is done reading from it.
>
> This caveat is now better explained in the documentation. See perldata.
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