For subs use the content of the @_, specially for big data sent to the function:
Don't use:
sub { my ($var1,$var2) = @_ ; }
The best way is to use the @_[0] it self or the shift:
sub { my $var1 = shift ; my $var2 = shift ; }
* If you use @_[?] you can't modifie it! Use shift if you need to write to the var.

I was pretty sure that was wrong when I read it, so I whipped out Benchmark:

#!/usr/bin/perl -w

use strict;
use Benchmark qw(cmpthese);

sub shifter {
    my $a=shift;
    my $b=shift;
    my $c=shift;
    my $d=shift;
    my $e=shift;
    my $f=shift;

    return $a*$b*$c*$d*$e*$f;
}

sub assigner {
    my ($a,$b,$c,$d,$e,$f)=@_;

    return $a*$b*$c*$d*$e*$f;
}

sub direct {
    return $_[0]*$_[1]*$_[2]*$_[3]*$_[4]*$_[5];
}

cmpthese(-5,
        {
             'shifter' => sub {shifter(1,2,3,4,5,6);},
             'assigner' => sub {assigner(1,2,3,4,5,6);},
             'direct'   => sub {direct(1,2,3,4,5,6);},
         }
     );
[download]

Results:

$ perl testSubs.pl
Benchmark: running assigner, direct, shifter, each for at least 2 CPU 
+seconds...

  assigner:  0 wallclock secs ( 2.06 usr +  0.02 sys = 2.08 CPU) @ 384
+577.33/s
(n=800690)
    direct:  3 wallclock secs ( 2.04 usr +  0.00 sys = 2.04 CPU) @ 629
+222.22/s
(n=1285501)
   shifter:  2 wallclock secs ( 2.09 usr +  0.00 sys = 2.09 CPU) @ 294
+563.31/s
(n=616521)
             Rate  shifter assigner   direct
shifter  294563/s       --     -23%     -53%
assigner 384577/s      31%       --     -39%
direct   629222/s     114%      64%       --
[download]

That's with perl 5.6.1... Maybe 5.8.0 optimized shift? But you'd have to keep the old values around and have a "front" entry in the AV, and I don't remember seeing anything about that.
--
Mike

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