#! /usr/bin/perl -w

use strict;
use POSIX;
use Benchmark;

sub via_anonsub {
  sub { sprintf '%04d%02d%02d%02d%02d%02d%05d',
    $_[5]+1900, $_[4]+1, $_[3], $_[2], $_[1], $_[0], $$
  }->(localtime())
}

sub via_sprintf {
  my @time = localtime();
  sprintf '%04d%02d%02d%02d%02d%02d%05d',
    $time[5]+1900, $time[4]+1, $time[3], $time[2], $time[1], $time[0], $$
}

sub via_concat {
  my @time = localtime();
  $time[4]++;
  $time[5]+=1900;
  $time[$_] = $time[$_]<10? "0".$time[$_]:$time[$_] for (0..5);
  my $filename = $time[5].$time[4].$time[3].$time[2].$time[1].$time[0].$$
}

sub via_posix {
  strftime( "%Y%m%d%H%M%S$$", localtime() )
}

print <<"PROOF";
via_concat:  ${\via_concat()}
via_anonsub: ${\via_anonsub()}
via_posix:   ${\via_posix()}
via_sprintf: ${\via_sprintf()}
PROOF

timethese( shift || 10000, {
  'via_anonsub' => \&via_anonsub,
  'via_concat'  => \&via_concat,
  'via_posix'   => \&via_posix,
  'via_sprintf' => \&via_sprintf,
});
##</code><code>##

$ perl filename 200000
via_concat:  2002091114542256876
via_anonsub: 2002091114542256876
via_posix:   2002091114542256876
via_sprintf: 2002091114542256876
Benchmark: timing 200000 iterations of via_anonsub, via_concat, via_posix, via_sprintf...
via_anonsub:  7 wallclock secs ( 5.60 usr +  0.28 sys =  5.88 CPU)
 via_concat: 21 wallclock secs (18.71 usr +  0.55 sys = 19.27 CPU)
  via_posix: 13 wallclock secs ( 9.59 usr +  0.62 sys = 10.20 CPU)
via_sprintf: 10 wallclock secs ( 6.67 usr +  0.39 sys =  7.06 CPU)

##</code><code>##

via_concat:  2002091114275977636
via_anonsub: 2002091114275977636
via_posix:   2002091114275977636
via_sprintf: 2002091114275977636
Benchmark: running via_anonsub, via_concat, via_posix, via_sprintf for at least 10 CPU seconds...
via_anonsub: 12 wallclock secs (10.12 usr +  0.51 sys = 10.62 CPU) @ 53156.42/s (n=564787)
 via_concat: 10 wallclock secs (10.20 usr +  0.24 sys = 10.44 CPU) @ 30435.83/s (n=317674)
  via_posix: 10 wallclock secs ( 9.57 usr +  0.93 sys = 10.50 CPU) @ 60954.29/s (n=640020)
via_sprintf: 10 wallclock secs (10.20 usr +  0.33 sys = 10.53 CPU) @ 44919.45/s (n=473058)
               Rate  via_concat via_sprintf via_anonsub   via_posix
via_concat  30436/s          --        -32%        -43%        -50%
via_sprintf 44919/s         48%          --        -15%        -26%
via_anonsub 53156/s         75%         18%          --        -13%
via_posix   60954/s        100%         36%         15%          --