How can I use Perl default array variable @_ with push?

Question

In the perlvar documentation there is a text about @_:

Within a subroutine the array @_ contains the parameters passed to that subroutine. Inside a subroutine, @_ is the default array for the array operators push, pop, shift, and unshift.

It is a common way to use shift without parameters to get first element from the array. It is very often used as:

sub some_method {
    my $self = shift; # the same as `my $self = shift @_;`

    ...
}

But in the documentation there is written that it can be used with push, but I can't create working example without explicitly specifying @_ to the push. From reading this doc I'm expecting push 123; to push to @_, but it is not working.

I've used perbug and send a messge. Here is that I have send — gist.github.com/bessarabov/2e938f4bbb79e78d1941 — bessarabov
– bessarabov, Commented Jun 21, 2015 at 13:21

Keith Thompson · Accepted Answer · 2018-09-11 18:31:37Z

11

I believe you've found an error in the documentation.

@_ is the default for pop and shift, but not for push and unshift. For both push and unshift, the array has to be specified explicitly.

perldoc -f push shows the syntax as:

push ARRAY,LIST
push EXPR,LIST

with no option to leave the array unspecified; likewise for perldoc -f unshift.

(The OP has submitted a Perl bug report; see https://gist.github.com/bessarabov/2e938f4bbb79e78d1941)

UPDATE:

This has been corrected. In the git repo for Perl, it was corrected in commit 256ca3d37ed232e10fbb2884be45691e745be7a9, 2015-06-21. The fix appears in releases 5.23.1 and 5.24.0. This doesn't seem to be mentioned in any of the perldelta*.pod files.

edited Sep 11, 2018 at 18:31

answered Jun 21, 2015 at 0:30

Keith Thompson

266k46 gold badges448 silver badges668 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How can I use Perl default array variable @_ with push?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related