sub natural_sort {
    my $i;
    s/(\d+)/pack 'aNa*', 0, length $1, $1/eg, $_ .= ' ' . $i++ for ( my @x = @_ );
    @_[ map { (split)[-1] } sort @x ];
}

print join ', ', natural_sort( map {"E$_"} (1..20) );