From: perl-win32-users-boun...@listserv.activestate.com
[mailto:perl-win32-users-boun...@listserv.activestate.com] On Behalf Of Greg
VisionInfosoft
Sent: 05 April 2013 21:16
To: Perl-Win32-Users@listserv.ActiveState.com
Subject: confused by use of 'implied' variable
> im butchering a public script i found on the internet for purpose of doing a
> CGI file upload.
Be very careful, there is a lot of poor quality scripts out there.
>
> theres one excerpt from the script that ive never used before. the few
> lines...
>
> while ( <$upload_filehandle> ) {
> print UPLOADFILE;
> }
>
> if it were me, i would not write code this way, i write in a way that make it
> easier for me to quickly
> understand what i was trying to do. if it were me coding this in my 'lame'
> (for idiots) way, it would look
> more like...
>
> while ( $data = <$upload_filehandle> ) {
> print UPLOADFILE $data;
> }
Not unreasonable, but you should restrict the scope of your variable to the
while loop.
while (my $data = <$upload_filehandle> ) {
etc.
>
> but now that ive seen the code, as originally presented, it does cause me to
> ask the question...
>
> how does one know under what set of circumstances can such 'abbreviated' code
> be written? in other words, how > can one know what kinds of features or
> operations can use the implied variable @_ (which I assume is the
> variable that would be used in this case).
The implied variable here is $_, not @_.
>
> specifically, if i wanted to append to a variable $aggregated_file_contents,
> each new block of the file as it > was being read and output...
>
> my thought was to try:
>
> while ( <$upload_filehandle> ) {
> print UPLOADFILE;
> $aggregated_file_contents.=;
You have to be explicit here. That is...
$aggregated_file_contents .= $_;
> }
>
> as opposed to what i would have normally done ($aggregated_file_contents .=
> $data;)
>
> yes, i know i can simply try it, to see if it works - but is there a more
> general rule one can follow that
> tells them when this kind of thing can normally be used, versus when not?
Start with 'perldoc perlvar'. It is the first one listed under General
Variables.
HTH
--
Brian Raven
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