=head1 TITLE
loop control and do
=head1 VERSION
Maintainer: Nathan Torkington <[EMAIL PROTECTED]>
Date: 1 Aug 2000
Version: 0 (unreleased)
Mailing List: [EMAIL PROTECTED]
Number: (unassigned)
=head1 ABSTRACT
In version 5 and earlier, C<do {} while> does not create a block.
Thus the loop controls C<next>, C<last>, and C<redo> do not work
inside C<do {} while>. In version 6 they should.
=head1 DESCRIPTION
The C<{}> in C<eval{}> and C<do{}> do not define blocks. This is a
problem because C<do {} while> is the only way to get a bottom-testing
"loop". This is not a real loop because the statement modifier version
of C<while> modifies the C<do> statement, not the non-block of code
in the C<{}>. Thus C<last>, C<next>, and C<redo> do not work on a
C<do {} while>.
However, they should. Just because you want to test the loop at the
bottom doesn't mean that don't want to break out of the loop early.
So a modified C<do{}> should count as a block.
I've used C<while>, but the same goes for C<until>.
=head1 IMPLEMENTATION
There are two implementation strategies: identify modified C<do>s,
or treat C<do {} while> as a different construct.
=head2 Identify modified do
If Perl builds a C<do {}> modified by C<while> or C<until>, it should
rewrite it to build a real block inside the C<do>ne code.
=head2 Different construct
Teach the parser that C<do {} while> is not a statement modifier,
but instead a full loop. That way the parser would construct the
block structure rather than requiring it to be grafted on later.
=REFERENCES
perlsyn for explanation of loops in Perl 5
