On Jan 12, 2008 1:50 PM, <[EMAIL PROTECTED]> wrote:
> Rob Dixon <[EMAIL PROTECTED]> writes:
>
> > which outputs "char<19>".
> >
> > If you're hoping for something different from this then perhaps you
> > would let us know.
>
> Sorry if I was unclear as to what I was after. Yes that was it.
>
> > 'bytes' is a pragma, and documentation on it can be retrieved in the
> > same way as for all pragma and modules by issuing
>
> > perldoc bytes
>
> And the bit about `perldoc bytes' was new ground for me too.
>
> I never ran into that usage I guess. Or never really thought to look
> a `pragma'.
>
> I thought, right along, that kind of syntax was reserved for pulling
> up documentation of a module, like `perldoc File::Find' or whatever.
> And have been confused about `pragma' as well.
>
> You've helped clear that up for me too.... thanks.
Well, a pragma is nothing more than a module that changes the behavior
of Perl (as opposed to adding functionality like normal modules). In
fact, here is the bytes pragma from Perl 5.8.4 (without the POD):
package bytes;
our $VERSION = '1.01';
$bytes::hint_bits = 0x00000008;
sub import {
$^H |= $bytes::hint_bits;
}
sub unimport {
$^H &= ~$bytes::hint_bits;
}
sub AUTOLOAD {
require "bytes_heavy.pl";
goto &$AUTOLOAD;
}
sub length ($);
sub chr ($);
sub ord ($);
sub substr ($$;$$);
sub index ($$;$);
sub rindex ($$;$);
1;
As you can see it is normal Perl. The real magic happens inside the
length and other functions. They check the value of the hints global
variable ($^H) and change their behavior if the "use bytes" bit is
set. In Perl 5.10 we have been given the ability to (safely) write
our own pragmas, see http://perldoc.perl.org/perlpragma.html for more
information, or if you have 5.10 installed you can say perldoc
perlpragma.
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