my @dirs = ('/dir1/', '/dir2/', '/dir3/', '/dir4/', '/dir5/', '/dir6/',);

my @newfiles = sort {-M $b <=> -M $a} grep {-f } glob("/main/*");
my @seq = (sort {-M $b <=> -M $a} @dirs) x int( 1 + @newfiles/@dirs);

for (@newfiles) {
    my $status = system '/bin/cp', '-f', $_, shift @seq;
    die 'Copy failed for ', $_, ': Child Error ', $?, $! if $status;
    unlink $_ unless $status;
}