I personally believe times could be ready for an argv pragma. Every now and again it occurs to me. The other day, in a reply I suggested a sub as follows:

sub domkfile {
    my $fname=shift;
    open my $fh, '<', $fname or die "Can't open `$fname': $!\n";
    join ' ' => map /SOURCE=\.\\(.*)$/i, <$fh>;
}

[download]

I was about to suggest that to make it more general, it may accept, rather than a single filename, a list of filenames, and take advantage of the magic *ARGV variables:

sub domkfile {
    local @ARGV = @_;
    join ' ' => map /SOURCE=\.\\(.*)$/i, <>;
}

[download]

Look! Even simpler! But then people would have complained: they always do. They say that a explicit opens are clearer. I beg to disagree: @ARGV and <> are deeply rooted mechanisms in the brain of every Perl programmer. Of course one may write a separate sub, or module -and perhaps some exist already (well, File::Slurp could be used here)- to slurp in lines from several files. But the above code is still more compact and yet clearly readable.

One argument I can buy, instead, is that the implicit open's associated with the ARGV filehandle are two args ones: while the implications of this are clear when it is used in a "top level" script (perhaps a very short one taking advantage of the -n or -p switches) and are often even desirable, its use in a sub, as in this case, can make them much more controversial.

Now, I think that this could be amended by an argv pragma which would locally change the nature of *ARGV's implicit open's, setting it explicitly to one type or the other, and perhaps do other thing, like setting layers. The above sub, e.g. could simply become:

sub domkfile {
    use argv '3args';
    local @ARGV = @_;
    join ' ' => map /SOURCE=\.\\(.*)$/i, <>;
}

[download]

A crazy idea?

--
If you can't understand the incipit, then please check the IPB Campaign.

In reply to How 'bout an argv pragma? by blazar

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