Re: What does "}{" mean?

On Fri, 2004-02-06 at 08:45, [email protected] wrote:
> What does the construct "}{" mean?  As in
> 
> 
>   $ perl -pe ' } { $_="foo\n"' /dev/null
>   foo
> 
> I figure it has to do with how the -p switch affects the script that
> is passed to the interpreter.  Is this documented anywhere?

perldoc perlrun:

       -n   causes Perl to assume the following loop around your
            program, which makes it iterate over filename argu-
            ments somewhat like sed -n or awk:

              LINE:
                while (<>) {
                    ...             # your program goes here
                }

            Note that the lines are not printed by default.  See
            -p to have lines printed.

The docs aren't speaking metaphorically; the while construct is
*literally* assembled around your code. So the example you gave above
results in:

    LINE:
      while (<>) {
        } { $_="foo\n"
      }

I think this might be documented more explicitly in perlfaq somewhere.

For a practical example, try this:

     perl -pe '}{print "$.\n"' .bashrc

(Substitute another filename for ".bashrc" if appropriate.)

-- 
Craig S. Cottingham
[email protected]