The -M operator returns the age in days wrt the script start time, so what you want can be as simple as this:

my $dir = '/path/to';
my $max_age = '5 days';
for (<$dir/*>) {
    -M > $max_age and print "I would have deleted $_.\n";
}
[download]

I could have set $max_age to numerical 5, but I like having the unit for self-documentation. As long as the numerals are first in the string, Perl does what I want.