-(void)someMethod {
    NSMutableArray *keywords = [[NSMutableArray alloc] init];
    NSError * err = nil;
    NSString *string = @"Hi, my name is Sam"
    //Building expression
    NSString * substring = [NSRegularExpression escapedPatternForString:@"am"];

    NSString *expression = [NSString stringWithFormat:@"\\S*?%@.*?\\b", substring];

    NSAutoreleasePool *innerPool = [[NSAutoreleasePool alloc] init];

    NSRegularExpression *regEx = [[NSRegularExpression alloc] initWithPattern:expression options:0 error:&err];
    [regEx enumerateMatchesInString:[string lowercaseString] options:0 range:NSMakeRange(0, [string length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){
        [keywords addObject:[string substringWithRange:[match range]]];
    }];
    [regEx release];
    [innerPool drain];

    //keywords not contains name and Sam
}