I found this bit odd:
Do not use shift. Use @_. shift is slower, and Brian has an allergic reaction to it.
        my $var = shift;                        # wrong
        my($var) = @_;                          # right
        sub foo { uc $_[0] }                    # OK
        my($var1, $var2) = (shift, shift);      # Um, no.

[download]
I always use shift, and I recall benchmarking it way back in the day before I made that decision, just to make sure it wasn't slower. Here's the test I used, and the results: 
use Benchmark qw(cmpthese);

sub x_shift
{
  while(@_)
  {
    my $a = shift;
  }
}

sub x_copy1
{
  for(my $i = 0; $i < $#_; $i++)
  {
    my $a = $_[$i];
  }
}

sub x_copy2
{
  my $end = $#_;

  for(my $i = 0; $i < $end; $i++)
  {
    my $a = $_[$i];
  }
}

my @args = (1 .. 100);

cmpthese(1000000, 
{ 
  x_shift => 'x_shift(@args)',
  x_copy1 => 'x_copy1(@args)',
  x_copy2 => 'x_copy2(@args)'
});

[download]
             Rate x_copy2 x_copy1 x_shift
x_copy2  609756/s      --    -18%    -45%
x_copy1  746269/s     22%      --    -32%
x_shift 1098901/s     80%     47%      --

[download]
Seeing the flat claim that shift is slower made me rethink my earlier test and try something more simple: 
use Benchmark qw(cmpthese);

sub x_shift { my $a = shift }
sub x_copy  { my $a = $_[0] }

my @args = (1 .. 3);

cmpthese(1000000, { x_shift => 'x_shift(@args)', x_copy => 'x_copy(@ar
+gs)' });

[download]
Sure enough, the results changed, but now it appears to be a tie: 
             Rate  x_copy x_shift
x_copy  1298701/s      --     -0%
x_shift 1298701/s      0%      --

[download]

The results fluctuate a few percent in each direction. Anyway, my point is that I don't think performance is a reason to avoid using shift.

(I have a whole directory of benchmarks for silly little things, e.g. benchmarking exists() vs. a test for truth on a hash key and crazy stuff like that. It's a disease...but it amuses me :-)

In reply to Re^2: I need perl coding standards by siracusa
in thread I need perl coding standards by kprasanna_79

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.