#! perl -sw
use strict;
use POSIX qw[strftime];

my $lastdate = 0 ;

while ( <STDIN> ) {
	my $now = strftime '%Y%m%d', localtime();
	if ( $lastdate ne $now ) {
		close STDOUT;
		open STDOUT, '>', "log$now" or die $!;
		$|++;
		$lastdate = $now;
	}
	print STDOUT '>', $_;
}