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stable on an ongoing basis.  Other functions will be added to C<builtin> over
time.

For details, see L<builtin>, but here's a summary of builtin functions in
v5.36:

=over 4

=item builtin::trim

This function treats its argument as a string, returning the result of removing
all white space at its beginning and ending.

=item builtin::indexed

This function returns a list twice as big as its argument list, where each item
is preceded by its index within that list. This is primarily useful for using
the new C<foreach> syntax with multiple iterator variables to iterate over an
array or list, while also tracking the index of each item:

    use builtin 'indexed';

    foreach my ($index, $val) (indexed @array) {
        ...
    }

=item builtin::true, builtin::false, builtin::is_bool

C<true> and C<false> return boolean true and false values.  Perl is still perl,
and doesn't have strict typing of booleans, but these values will be known to
have been created as booleans.  C<is_bool> will tell you whether a value was
known to have been created as a boolean.

=item builtin::weaken, builtin::unweaken, builtin::is_weak

These functions will, respectively: weaken a reference; strengthen a reference;
and return whether a reference is weak.  (A weak reference is not counted for
garbage collection purposes.  See L<perlref>.)  These can take the place of
some similar routines in L<Scalar::Util>.

=item builtin::blessed, builtin::refaddr, builtin::reftype

These functions provide more data about references (or non-references,
actually!) and can take the place of similar routines found in L<Scalar::Util>.

=item builtin::ceil, builtin::floor

C<ceil> returns the smallest integer greater than or equal to its argument.
C<floor> returns the largest integer less than or equal to its argument.  These
can take the place of similar routines found in L<POSIX>.

=back

=head2 C<defer> blocks (experimental)

This release adds support for C<defer> blocks, which are blocks of code
prefixed by the C<defer> modifier. They provide a section of code which runs
at a later time, during scope exit.

In brief, when a C<defer> block is reached at runtime, its body is set aside to
be run when the enclosing scope is exited.  It is unlike a UNITCHECK (among
other reasons) in that if the block I<containing> the C<defer> block is exited
before the block is reached, it will not be run.

C<defer> blocks can be used to take the place of "scope guard" objects where an
object is passed a code block to be run by its destructor.

For more information, see L<perlsyn/"defer blocks">.

=head2 try/catch can now have a C<finally> block (experimental)

The experimental C<try>/C<catch> syntax has been extended to support an
optional third block introduced by the C<finally> keyword.

    try {
        attempt();
        print "Success\n";
    }
    catch ($e) {
        print "Failure\n";
    }
    finally {
        print "This happens regardless\n";
    }

This provides code which runs at the end of the C<try>/C<catch> construct,
even if aborted by an exception or control-flow keyword. They are similar
to C<defer> blocks.

For more information, see L<perlsyn/"Try Catch Exception Handling">.

=head2 non-ASCII delimiters for quote-like operators (experimental)

Perl traditionally has allowed just four pairs of string/pattern
delimiters: S<C<( )>> S<C<{ }>> S<C<[ ]>> and S<C<< < > >>>, all in the
ASCII range.  Unicode has hundreds more possibilities, and using this
feature enables many of them.  When enabled, you can say S<C<qr« »>> for
example, or S<C<use utf8; q𝄃string𝄂>>.  See L<feature/The
'extra_paired_delimiters' feature> for details.

=head2 @_ is now experimental within signatured subs

Even though subroutine signatures are now stable, use of the legacy arguments
array (C<@_>) with a subroutine that has a signature I<remains> experimental,
with its own warning category.  Silencing the C<experimental::signatures>
warning category is not sufficient to dismiss this.  The new warning is emitted
with the category name C<experimental::args_array_with_signatures>.

Any subroutine that has a signature and tries to make use of the defaults
argument array or an element thereof (C<@_> or C<$_[INDEX]>), either
explicitly or implicitly (such as C<shift> or C<pop> with no argument) will
provoke a warning at compile-time:

    use v5.36;

    sub f ($x, $y = 123) {
      say "The first argument is $_[0]";
    }

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