Re: s/// w/o intermediate variables?

On 2004-05-04, at 11:13:38 -0400, [email protected] wrote:

> Here's an example of a recurrent annoyance:
> 
>   my $package = 'Foo::Bar::Baz';
>   (my $package_filename = $package) =~ s,::,/,g;
>   require $package_filename;
>   $package->foobar();
> 
> One of my many neurotic little peeves is that, unless code readability
> absolutely demands it, I hate defining variables that will be used
> only once, such as $package_filename above.  I would like to be able
> to do something like
> 
>   my $package = 'Foo::Bar::Baz';
>   require TRANSFORM[ s,::,/,g, "$package.pm" ];
>   $package->foobar();
> 
> where TRANSFORM[] stands for an expression in which an "s-expression"
> (i.e. one using s///) is applied to a string, and the resulting string
> is returned as the result.
> 
> Of course, I could define a helper sub to do this:
> 
>   sub transform {
>     my $s_expression = shift;
>     local $_ = shift;
>     eval $s_expression;
>     die $@ if $@;
>     $_
>   }
> 
> But is there a way to achieve this result without defining such a
> helper sub?

Something like

  mhx@r2d2 ~ $ cat /tmp/xxx.pl 
  my $package = 'Data::Dumper';
  require do { my $_="$package.pm"; s,::,/,g; $_ };
  print $package->Dump([$package]);

  mhx@r2d2 ~ $ bleadperl /tmp/xxx.pl 
  $VAR1 = 'Data::Dumper';

?

Ok, it uses $_, but only scoped, and $_ is there anyway.

(You may s/my \$_/local \$_/ for backwards compatibility.)

Marcus

> kynn
> 
> P.S. I couldn't come up with a sufficiently general transform sub such
> that its first argument is a qr-quoted regexp.  Is there a way to do
> this that approaches the level of generality of the eval kluge above?
> 


-- 
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SCSI's too wide.