foreach my $day(0..15){     
     my @ymd = (localtime(time - 3600*24*$day))[5,4,3];  # build up an array of just year,month and day, n days backward
     say join'-',$ymd[0]+1900,(sprintf '%02d',$ymd[1]+1),(sprintf '%02d',$ymd[2]);   #print them in the format you need
}   

2018-01-03
2018-01-02
2018-01-01
2017-12-31
2017-12-30
2017-12-29
2017-12-28
2017-12-27
2017-12-26
2017-12-25
2017-12-24
2017-12-23
2017-12-22
2017-12-21
2017-12-20
2017-12-19


##</code><code>##

# untested...
foreach my $filepath (@paths){

   open my $fh,'<', $filepath or die "unable to open $filepath!";
   while (<$fh>){
       if($_ =~ /$usr_supplied_regex/){
           print "$filepath:$.".$_;
       }
   }

}