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All built-in functions that operate directly on array or hash
containers now also accept hard references to arrays or hashes:
|----------------------------+---------------------------|
| Traditional syntax | Terse syntax |
|----------------------------+---------------------------|
| push @$arrayref, @stuff | push $arrayref, @stuff |
| unshift @$arrayref, @stuff | unshift $arrayref, @stuff |
| pop @$arrayref | pop $arrayref |
| shift @$arrayref | shift $arrayref |
| splice @$arrayref, 0, 2 | splice $arrayref, 0, 2 |
| keys %$hashref | keys $hashref |
| keys @$arrayref | keys $arrayref |
| values %$hashref | values $hashref |
| values @$arrayref | values $arrayref |
| ($k,$v) = each %$hashref | ($k,$v) = each $hashref |
| ($k,$v) = each @$arrayref | ($k,$v) = each $arrayref |
|----------------------------+---------------------------|
This allows these built-in functions to act on long dereferencing
chains or on the return value of subroutines without needing to wrap
them in C<@{}> or C<%{}>:
push @{$obj->tags}, $new_tag; # old way
push $obj->tags, $new_tag; # new way
for ( keys %{$hoh->{genres}{artists}} ) {...} # old way
for ( keys $hoh->{genres}{artists} ) {...} # new way
For C<push>, C<unshift> and C<splice>, the reference will auto-vivify
if it is not defined, just as if it were wrapped with C<@{}>.
Calling C<keys> or C<values> directly on a reference gives a
substantial performance improvement over explicit dereferencing.
For C<keys>, C<values>, C<each>, when overloaded dereferencing is
present, the overloaded dereference is used instead of dereferencing
the underlying reftype. Warnings are issued about assumptions made in
the following three ambiguous cases:
(a) If both %{} and @{} overloading exists, %{} is used
(b) If %{} overloading exists on a blessed arrayref, %{} is used
(c) If @{} overloading exists on a blessed hashref, @{} is used
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