use warnings;
use strict;

while (<DATA>) {
	print "$1\n" if /(?<=\s)([a-z\s]+)(?=\s)/i;

}

__DATA__
1) some text 2)
1. some text 2.
1) some text 2.
1. 2.10.10.20 some text 2.
1) 2.10.10.20 2)