in reply to Re^2: How 'bout an argv pragma?
in thread How 'bout an argv pragma?

So you think localizing @ARGV should also localize the (potentially open) ARGV filehandle too? Maybe I'm not understanding you, but that doesn't make a lot of sense to me.

What exactly did you try? Localizing *ARGV worked for me exactly as I would have thought: 

$ cat ../domk.pl
#!/usr/bin/perl

use strict;
use warnings;

while (<>) {
    chomp;
    print "huzzah:".collect( $_ )."!\n";
}

sub collect {
    local *ARGV;
    @ARGV = @_;
    join '', <>;
}

$ ls file? | ../domk.pl
huzzah:file1 line1
file1 line2
!
huzzah:file2 line1
file2 line2
!

[download]
--
Online Fortune Cookie Search

Replies are listed 'Best First'.
Re^4: How 'bout an argv pragma?
by blazar (Canon) on May 28, 2008 at 10:01 UTC
    So you think localizing @ARGV should also localize the (potentially open) ARGV filehandle too?

    I personally believe that based on the principle of least surprise, I would indeed say so. Perl does magic worse than that already, and otherwise a localised @ARGV would be of little utility since one would want to use the above described technique (referring to your sub) as a cheap shortcut to

    sub collect {
    join '', map {
        open my $fh, '<', $_ or warn "Can't open `$_': $!\n";
        <$fh>;
    } @_;
}

    [download]

    (But for the 2-args implicit openedness, of course.)

    What exactly did you try? Localizing *ARGV worked for me exactly as I would have thought:

    It doesn't work for me:

    Read more... (885 Bytes)

    But even if it did "work", as it did with you and kyle, it wouldn't be much dwimmy: in fact your output is not the same one would have got out of using the "expanded" sub above. The following example won't work on my box either, but you could try it:

    Read more... (597 Bytes)

    Update: dopen has issues; this was discussed in another thread.

    --
    If you can't understand the incipit, then please check the IPB Campaign.
[reply]
[d/l]
[select]
      I would be much more surprised to have localizing @ARGV affect *ARGV{IO}, but I can see how you could feel otherwise. But I'm not sure this kind of dwimmery is effective; there is a similar, documented dwim when you localize $., but I think that's so little known as to be almost pointless.

      Your test passes for me on perl, v5.8.8 built for i486-linux-gnu-thread-multi; I'll try to experiment with other versions when I have more time.

      --
      Online Fortune Cookie Search
[reply]

        I personally believe that localizing @ARGV only without the rest would be of little to no utility at all, and intuitively it should do what I thought. Well, at least Juerd thought so, too. (Thanks to BrowserUk, who let me know.) Further, people can start to play with (most common) predefined variables and local early, but learn about typeglobs only much later. Actually I think that $Larry now believes they were not a nice idea at all, and that's why they are going away in Perl 6; more precisely here's what he said:

        Nope, typeglobs are dead, dead, dead, dead, and dead, not necessariy in that order.
        --
        If you can't understand the incipit, then please check the IPB Campaign.
[reply]
[d/l]
[select]

In Section Meditations