slightly faster to do ... * 86400

No, any good optimizer should optimize away those multiplications (in any language) anyway (so if its done in a loop it shouldn't matter, and if its only done once then it makes too little difference to matter), and its better self-documentation IMHO to leave it as '24*60*60' because those numbers mean something to me, whereas 86400 does not. Someone could inadvertently change it to 84600 and I wouldn't notice the difference until many wrong calculations had been done. In any case, this is a bad place for micro-optimizations...

It makes it obvious what is meant and makes no significant difference to speed whatsoever:

use Benchmark;

$yours = '
$days = 10;
$then = localtime(time() + $days * 86400);';

$mine = '
$days = 10;
$then = localtime(time() + $days * 24*60*60 );';

timethese ( 100000, { 'yours' => $yours, 'mine' => $mine } );
__END__
Benchmark: timing 100000 iterations of mine, yours...
      mine: 30 wallclock secs (29.95 usr +  0.00 sys = 29.95 CPU) @ 33
+38.89/s (n=100000)
     yours: 30 wallclock secs (29.94 usr +  0.00 sys = 29.94 CPU) @ 33
+40.01/s (n=100000)
[download]

sleep 28800 :-) cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

It makes a bit more difference if you factor in compile time (more tokens to parse, and no optimization of multiplying constants, don't ask me which makes more of a difference):

use strict;
use warnings;

use Benchmark;
my $x = 5;

timethese(-5, {
 EXPANDED=>sub { eval '$x * 24 * 60 * 60' },
 NOT_EXP =>sub { eval '$x * 86400' },
});

Benchmark: running EXPANDED, NOT_EXP, each for at least 5 CPU seconds.
+..
  EXPANDED:  6 wallclock secs ( 5.31 usr +  0.00 sys =  5.31 CPU) @ 56
+77.40/s (n
=30147)
   NOT_EXP:  6 wallclock secs ( 5.26 usr +  0.00 sys =  5.26 CPU) @ 67
+49.24/s (n
=35501)
[download]

But of course I'd leave in the explicit multiplications anyway for reasons already mentioned. If I really needed to eval that, I might put something like $seconds_per_day = 24 * 60 * 60; outside of the eval, then use the variable inside.