my @MATCH_RE = ( 
  q%(?:this|or|that)%,
);

my @MATCH_REC = map { qr/$_/ } @MATCH_RE;

sub doit {
  my($str) = @_;
  
  for my $re (@MATCH_REC) {
      return 0 if $str =~ m%$re%i;
  }
  return 1;
}

##</code><code>##

my @SUB_RE = ( 
  q@%(?:this|or|that)%bob%gsi@,    
  q@%(?:One|Two|Three)%Four%gs@,  # note different modifier
);

# or, with 's' embedded
my @SUB_RE2 = ( 
  q@s%(?:this|or|that)%bob%gsi@,    
  q@s%(?:One|Two|Three)%Four%gs@,  # note different modifier
);


my @SUB_REC = map { qr/$_/ } @SUB_RE;

sub doit {
  my($str) = @_;
  
  for my $re (@SUB_REC) {
      $str =~ $re;
  }
  return $str;
}