G'day fionbarr,

[Note: When making references to publications it's good practice to specify edition, chapter and page. In this case: Advanced Perl Programming, 1st Edition - Chapter 3: Typeglobs and Symbol Tables - Page 44]

This is a cut-down version of code from a section that starts:

Efficient parameter passing

Aliases happen to be quite a bit faster than references, because they don't need to do any dereferencing. ...

I found typeglob aliases to be ~40% faster than references. Here's an average Benchmark:

$ perl -Mstrict -Mwarnings -E '
    use Benchmark qw{cmpthese};
    my @original_array = (10, 20);
     
    sub glob_double {
        local *copy = shift;
        for (@::copy) {
            $_ *= 2;
        }           
    }    
     
    sub ref_double {
        my $array_ref = shift;
        for (@$array_ref) {
            $_ *= 2;
        }           
    }    
     
    cmpthese(-1 => {
        glob => sub { @::array = @original_array; glob_double(*array) 
+},
        ref  => sub { my @array = @original_array; ref_double(\@array)
+ },
    });                                                               
+   
'
         Rate  ref glob
ref  546132/s   -- -28%
glob 763738/s  40%   --
[download]

Almost identical code, along with a discussion, can be found in "perlsub - Passing Symbol Table Entries (typeglobs)".