Why is there no low-precedence equivalent to // in Perl?

Question

I suppose this question may strike some as not very important, but I have been wondering why there is no low-precedence defined-or operator in Perl. I suppose there is a reason, since perlop explicitely mentions the fact.

One instance where I would think it useful is in such a subroutine:

sub input_many_data {
    my $x = <> // return;
    do_some_processing_with($x);
    my $y = <> // return;
    do_some_processing_with($y);
    return ( $x, $y );
}

while (1) {
    my ( $x, $y ) = &input_many_data or last;
    do_something_with( $x, $y );
}

It does work with $x = (<> // return), but the purpose would be much more obvious, and the code more readable and less error-prone, with something like ($x = <>) dor return.

Answer 1

I never really understood why some porters^[1] had a problem with it. I think there was a lack of consensus about what to call it (definedor, dor, err), but in retrospect, I'd be tempted to believe the true reason is a lack of comfort with use feature. Keep in mind that use feature and // were added to Perl in the same version.

Or maybe not. You can find the conversation on the p5 porters mailing list.

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By the way, the intent of the following is quite obvious:

my $x = <>
   // return;

It's a bad practice to hide a return at the end of a line anyway. Alternatives are:

( my $x = <> )
   // return;

defined( my $x = <> )
   or return;

my $x = <>;
$x // return;

my $x = <>;
return if !defined($x);

Those of those are compatible with commonly used 5.8.

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1. Those who work on Perl itself.