The POSIX module also provides the strftime() function, which is very convenient to use in this case as well:

use strict;
use POSIX qw(strftime);

sub local_yyyymmdd {
  my ($time) = shift || time;
  return strftime( '%Y-%m-%d', localtime($time));
};
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Documentation on strftime is pretty scarce, as it is the C function of the same name, but the DateTime module has a similar function which takes similar parameters in the format string.

Updated: Added dashes thanks to ysth, added paragraph about the documentation

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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