my $datetime = '2009-09-22 20::45::30';
printf('%3$s/%2$s/%1$s[%4$s::%5$s::%6$s]'."\n",
    $datetime =~ /(\d+)/g
);

##</code><code>##

my $datetime = '2009-09-22 20::45::30';
printf("%s/%s/%s[%s::%s::%s]\n",
    ( $datetime =~ /(\d+)/g )[2,1,0,3,4,5]
);

##</code><code>##

my $datetime = '2009-09-22 20::45::30';
(my $print_date = $datetime) =~
    s{(\d+)-(\d+)-(\d+) (.*)}{$3/$2/$1\[$4]};
print("$print_date\n");