my @list = map {"E$_"} (1..20);

for my $k (sort {substr($a, 1) <=> substr($b, 1)} @list) {
	print "$k ";
}

##</code><code>##

my @list = ("A15", "Y2", map {"E$_"} (1..20));

for my $k (
	map {$_->[0]} 
	sort {$a->[1] cmp $b->[1] || $a->[2] <=> $b->[2]} 
	map {[$_, /(\D+)(\d+)/]} 
	@list
) {
	print "$k ";
}