$ > xxx 2> yyy
$ perl -Mstrict -Mwarnings -E '
    sub same_mod_time { (stat($_[0]))[9] == (stat($_[1]))[9] }
    say same_mod_time(qw{xxx yyy}) ? "same" : "different";
'
same

$ > xxx
$ perl -Mstrict -Mwarnings -E '
    sub same_mod_time { (stat($_[0]))[9] == (stat($_[1]))[9] }
    say same_mod_time(qw{xxx yyy}) ? "same" : "different";
'
different

$ rm xxx yyy
$