use warnings;
use strict;

my @files = qw(
	3_xy.txt
	10_foo.txt
	2_bar.txt
	1_foobar.txt
	5_anton.txt
	7_berta.txt
	9_claus.txt
);

@files =
	map  { join('_', $_->[0], $_->[1]) }
	sort { $a->[1] cmp $b->[1] }
	map  { [/^(.*)_(.*)$/]  } @files;

foreach my $file (@files){
	print "$file\n";
}