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.

Answer 1

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.