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

From the keyboard of [email protected] [04.05.04,11:13]:

>
>
>
>
> 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?

what you require is a modifier for the s/// operator (perhaps 'r') which
makes s/// return the transformed string as a result rather than the
number of occurences of the pattern, assigning the value of a variable to
a local $_ (for the s/// operator to work with) and storing the result in
a kin of the builtins $_,$',$` and $& - let's assume $§:

$package = s,::,/,gr; # assign $package to $_, do the s/// and store result
require $§;

AFAIK there's no such thingy. All you can do is storing the resulting
strings elsewhere (in a local $_ for instance) or have it being returned
by some helper function.

I might be wrong :-)

> 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?

I guess, no, because you can't pass the modifiers to s/// as a variable
like so

s/$pat/$repl/$mod

Again, I might be wrong...

greets,
georg

-- 
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                              /\_¯/(q    /
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