SPUG: spug: What is the idiomatic way to extract first/last item after split?

[Colin Meyer]

[I meant to send this reply to the list ...]

On Tue, Jun 28, 2005 at 03:00:38PM -0700, Uri London wrote:
> 
> What is the idiomatic way to extract first/last item after split?
> 
> More interestingly, why #2 doesn't work, while #3 does?
> 
> For example:
> 
> $path = `cd`;
>  
> 
> # 1. working, but I've been told not very efficient:
> 
> $base = (split /\\/, $path)[-1];
> 

This is plenty efficient. To compare efficency, see the
Benchmark module.

> 
> # 2. this isn't working for me. Why???
> 
> $base = pop split /\\/, $path;

pop only works on an array. An array variable stores a list,
but a list isn't the same as an array.

You could create an annonymous array reference, and dereference
it, but it gets to look fairly ugly:

  $base = pop @{ [ split /\\/, $path ] };

> 
> # 3. This is similar to above, but does work.
> 
> @tmp = split /\\/, $path;
> 
> $base = pop @tmp;

This works because your are storing the list in an array, which
then works as expected with pop().

> 
> # 4. Work, but I believe slower:
> 
> ($base) = $path =~ /.*\\([^\\])/;

Try playing Benchmark. Then you can know instead of believing. You
can believe me when I say that it's more satisfying to know. :)

It really is well worth your time to do simple benchmarks. After using
Perl heavily for more than 10 years, I am still sometimes surprised
by benchmarking similar ways of doing things.

Have fun,
-Colin.