$ perl -Mstrict -Mwarnings -E '
    my $file = q{pm_1030903.dummy};
    say "(stat \$file)[9] = ", (stat $file)[9];
    say "15 mins. ago = ", time - 60 * 15;
    if ( (stat $file)[9] < time - 60 * 15 ) {
        say "[stat] Will delete $file";
    }
    say "-C \$file = ", -C $file;
    say "15 mins. in days = ", 60*15 / (24*60*60);
    if ((-C $file) > 60*15 / (24*60*60)) {
        say "[-C] Will delete $file";
    }
'
(stat $file)[9] = 1367039733
15 mins. ago = 1367041074
[stat] Will delete pm_1030903.dummy
-C $file = 0.0151736111111111
15 mins. in days = 0.0104166666666667
[-C] Will delete pm_1030903.dummy