Small oversight - your benchmark with $unused never makes an assignment from @_. When I fixed the typo and reran it, (undef, $x)= @_ was marginally faster than ($unused, $x) = @_ though not by an amount I consider significant (3%). -- Tested on Perl 5.10.0, system Perl for Debian Lenny, 32bit.

use Benchmark qw(cmpthese);

my $a1='a'x1e6;
my $b1=12345;
cmpthese -1,{
    a=>q[ sub{ my( undef, $x) = @_ }->( $a1, $b1 ) ],
    b=>q[ sub{ my $x = $_[1]        }->( $a1, $b1 ) ],
    c=>q[ sub{ my( $unused, $x ) = @_;}->( $a1, $b1 ) ],
};

# Output
      Rate    c    a    b
c 649176/s   --  -3% -33%
a 670690/s   3%   -- -30%
b 963764/s  48%  44%   --

[download]

Update added Perl version and platform; clarified ranking of results.

In reply to Re^2: Is undef list assignment a no-op? by ELISHEVA
in thread Is undef list assignment a no-op? by repellent

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