stefp,

Let's look at the numbers: 

#!/usr/local/bin/perl
use Benchmark;

use constant DEBUG_C => (1);
sub DEBUG_S() { 1 }
$DEBUG_V = 1;


timethese( 4000000, {
        'constant'   => sub { my $x = 1 if DEBUG_C; my $y=2; },
        'subroutine' => sub { my $x = 1 if DEBUG_S; my $y=2; },
        'variable'   => sub { my $x = 1 if $DEBUG_V; my $y=2; },
  }
);

[download]
produces the following (for DEBUG set to 1 and 0) 
DEBUG 0, Run 1
Benchmark: timing 4000000 iterations of constant, subroutine, variable...
  constant:  3 wallclock secs ( 2.00 usr +  0.01 sys =  2.01 CPU) @ 1990049.75/s (n=4000000)
subroutine:  3 wallclock secs ( 1.99 usr +  0.00 sys =  1.99 CPU) @ 2010050.25/s (n=4000000)
  variable:  5 wallclock secs ( 3.93 usr +  0.00 sys =  3.93 CPU) @ 1017811.70/s (n=4000000)

DEBUG 0, Run 2
Benchmark: timing 4000000 iterations of constant, subroutine, variable...
  constant:  1 wallclock secs ( 1.99 usr +  0.00 sys =  1.99 CPU) @ 2010050.25/s (n=4000000)
subroutine:  1 wallclock secs ( 2.13 usr +  0.00 sys =  2.13 CPU) @ 1877934.27/s (n=4000000)
  variable:  3 wallclock secs ( 3.85 usr +  0.00 sys =  3.85 CPU) @ 1038961.04/s (n=4000000)

DEBUG 0, Run 3
Benchmark: timing 4000000 iterations of constant, subroutine, variable...
  constant:  1 wallclock secs ( 2.07 usr +  0.00 sys =  2.07 CPU) @ 1932367.15/s (n=4000000)
subroutine:  1 wallclock secs ( 2.19 usr +  0.00 sys =  2.19 CPU) @ 1826484.02/s (n=4000000)
  variable:  3 wallclock secs ( 3.78 usr +  0.00 sys =  3.78 CPU) @ 1058201.06/s (n=4000000)

DEBUG 1, Run 1
Benchmark: timing 4000000 iterations of constant, subroutine, variable...
  constant:  8 wallclock secs ( 7.47 usr +  0.00 sys =  7.47 CPU) @ 535475.23/s (n=4000000)
subroutine:  8 wallclock secs ( 7.49 usr +  0.00 sys =  7.49 CPU) @ 534045.39/s (n=4000000)
  variable:  9 wallclock secs ( 9.13 usr +  0.00 sys =  9.13 CPU) @ 438116.10/s (n=4000000)

DEBUG 1, Run 2
Benchmark: timing 4000000 iterations of constant, subroutine, variable...
  constant:  8 wallclock secs ( 7.53 usr +  0.00 sys =  7.53 CPU) @ 531208.50/s (n=4000000)
subroutine:  7 wallclock secs ( 7.41 usr +  0.00 sys =  7.41 CPU) @ 539811.07/s (n=4000000)
  variable:  8 wallclock secs ( 9.27 usr +  0.00 sys =  9.27 CPU) @ 431499.46/s (n=4000000)

DEBUG 2, Run 3
Benchmark: timing 4000000 iterations of constant, subroutine, variable...
  constant:  8 wallclock secs ( 7.38 usr +  0.00 sys =  7.38 CPU) @ 542005.42/s (n=4000000)
subroutine:  8 wallclock secs ( 7.23 usr +  0.00 sys =  7.23 CPU) @ 553250.35/s (n=4000000)
  variable:  9 wallclock secs ( 9.06 usr +  0.00 sys =  9.06 CPU) @ 441501.10/s (n=4000000)
Looking at those numbers - sure $DEBUG is a bit slower but I'd say the savings are a wash - especially if there's some network or database code also in the script. The amount of time you save from not using $DEBUG is really down in the noise. The key here is to choose one method and be consistent with it's application across all scripts/modules in your project(s).

-derby

In reply to Re: inlined DEBUG constant versus $DEBUG by derby
in thread inlined DEBUG constant versus $DEBUG by stefp

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.