sub timestamp {
  return localtime (time);
}

print '[' . timestamp() . ']: Normal Time Format'. "\n";

##</code><code>##

[Sat Jan  8 11:59:07 2011]: Normal Time Format

##</code><code>##

use Time::localtime;
sub timestamp {
  my $t = localtime;
  return sprintf( "%04d-%02d-%02d_%02d:%02d:%02d",
                  $t->year + 1900, $t->mon + 1, $t->mday,
                  $t->hour, $t->min, $t->sec );
}

print '[' . timestamp() . ']: Custom Time Format'. "\n";

##</code><code>##

[2011-01-08_12:06:05]: Custom Time Format