use strict;
use warnings;
use Data::Dumper;

my $str1 = q!AND (random text) AND (more random text) AND (yet more)!;
my $str2 = q!OR (random text) OR (more random text) OR (yet (more))!;

for ( $str1, $str2 ) {
    my @texts = grep $_          # filter out empty strings
        , split /
                 (?:\)\s|^)      # either closing parentheses or start of string
                 (?:AND|OR)\s\(  # followed by AND or OR and opening parentheses
                 |               #   or 
                 \)$             # closing parentheses at end of string
                /x;
    print Dumper \@texts;
}