# first num
sub num_from_str {
    my $str = shift;
    my ($num) = $str =~ /(\d+)/;
    return $num;
}
my @a = qw( ch1 ch11 ch55 ch5 ch2 ch16 );
my @sorted = sort { num_from_str($a) <=> num_from_str($b) } @a;
print "$_\n" for @sorted;