Reverse filename order by a given range

rev_no.pl

#!/usr/bin/perl -w
use File::Copy;
use utf8;
use strict;

my $usage = "Usage: $0 from to.";
if (not defined $ARGV[0] or not defined $ARGV[1]) {
	die "$usage\n";
}

my $from_no = $ARGV[0];
my $to_no = $ARGV[1];
if ($from_no !~ /^\d+$/ or $to_no !~ /^\d+$/ or $from_no >= $to_no) {
	die "$usage\n";
}
my $len = (length $from_no > length $to_no ? length $from_no : length $to_no);
if ($len < 2) { $len = 2; }
my $pattern = '%0'.$len.'d';

my @files = <*>;
@files = sort @files;

my $range_pat;
for my $ii ($from_no .. $to_no) {
	$range_pat .= (sprintf '%0'.$len.'d', $ii).'|';
}
chop $range_pat;

@files = grep {m/.?($range_pat)\.jpg/i} @files;

my $i = 0;
my @files2;
for my $f (@files) {
	my $rep = sprintf "%0".$len."d_", $to_no - ($i++);
	$f =~ m/^(.*)(\d{$len})(\.jpg)$/i;
	my $new_f = $1.$rep.$3;
	push @files2, $new_f;
	move($f, $new_f) || die "move: $!";
}

$i = 0;
for my $f (@files2) {
	#my $rep = sprintf "%0".$len."d", $from_no + ($i++);
	$f =~ m/^(.*)(\d{$len})_(\.jpg)$/i;
	my $new_f = $1.$2.$3;
	move($f, $new_f) || die "move: $!";
}