The problem with regex101 is the explaination is not so easy to read. It contains some extra helpful information like a list of "whitespace characters". Try this: \s+HelloWorld\s+
The OP's tool seems better at explaining, though the "one or more times" could be said in repeat much earlier.
Pretty cool. One minor bug: it says "repeat" for "?", but then for the number of times it says "optional". It really shouldn't say "repeat" at all for that character.
Pretty nice. It could deal with weird java specific stuff like for example \p{javaWhitespace} - it deals with \s by saying it is "any whitespace", but it seems to think \p{javaWhitespace} is a character sequence, rather than an odd java-specific character class.