RegexFaster.apex

// Randomly select A-Z, a-z, 0-9
String randomStringAllEnhanced(Integer count) {
    Integer[] chars = new Integer[0],
        offsets = new Integer[] { 48, 65, 97 },
		mods = new Integer[] { 10, 26, 26 };
    while(count > chars.size()) {
    	Integer rnd = Math.abs(Crypto.getRandomInteger()), cat = Math.mod(rnd, 3), seed = Math.mod(rnd, mods[cat]);
        chars.add(seed+offsets[cat]);
    }
    return String.fromCharArray(chars);
}
// Configurable values to see the effects
Integer limitValue = 1000;
Integer searchValue = limitValue/10;

String[] searchwords = new String[0];
String[] allwords = new String[0];

// Create random words
for(Integer i = 0; i < searchValue; i++) {
    searchwords.add(randomStringAllEnhanced(10));
}
for(Integer i = 0; i < limitValue; i++) {
    allWords.add(randomStringAllEnhanced(10));
}
// Make sure some searchWord values are in allWords
for(Integer i = 0; i < searchValue; i++) {
    allWords[(Math.random()*limitValue).intValue()] = searchWords[(Math.random()*searchValue).intValue()];
}
// Nice, long | separated list of values for regexp
String searchTerm = String.join(searchwords,'|');
Long stop1 = DateTime.now().getTime();
Pattern p = Pattern.compile(searchTerm);
for(String searchString: allwords) {
    Boolean m = p.matcher(searchString).find();
}
Long stop2 = DateTime.now().getTime();
for(String searchString: allwords) {
    // Search each term for each possible word, some chance of matching
    for(String containsSearchTerm: searchWords) {
    	Boolean s = searchString.contains(containsSearchTerm);
        if(s) { // We found a match
            break;
        }
    }
}
Long stop3 = DateTime.now().getTime();
System.debug('Substring: ' + (stop3-stop2) + 'ms');
System.debug('Regexp: ' +(stop2-stop1)+'ms');