my $times = $ARGV[1];
my ($start_time, $end_time) = ( $times =~ /^(\d{6})-(\d{6})$/ ) or die "Time values are not in correct form\n";

my $dates = $ARGV[2] ||
    strftime ("%y%m%d", localtime); # make sure to use POSIX qw(strftime);

my $start_date, $end_date;
if ( ! (($start_date, $end_date) = ( $dates =~ /^(\d{6})-(\d{6})$/ ) ) ) {
   ( $start_date ) = ( $dates =~ /^(\d{6})$/ ) or die "Date values not in correct form";
   $end_date = $start_date;
}

##</code><code>##

my @matched;
foreach $file ( @filelist ) {   # or a while loop...
    my ( $fdate, $ftime ) = ( $file =~ /(\d{6})(\d{6})$/ );
    if ( ( $fdate >= $start_date ) && ( $fdate <= $end_date ) 
         && ( $ftime >= $start_time ) && ( $ftime <= $end_time) ) {
      push @matched, $file;
    }
}