I like to use the core module Time::Local to check for time differences.

use Time::Local qw( timelocal_nocheck );

my ($mday, $mon, $year) = (localtime())[3, 4, 5];
my $five_days_ago = timelocal_nocheck(0, 0, 0, $mday-5, $mon, $year);

foreach my $filename (...) {
   next unless (stat($filename))[9] < $five_days_ago;

   ...do something...
}
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