As I said before, it was pointed out elsewhere in this
thread. In one of my postings, I showed a program pointing
out the differences. Please read the entire thread - it's
not that there are 500 postings.
Thanks Abigail, I have realised the problem of my mistake, where the double space is matched as "space + not <". My previous regular expression should really be written as /_test\s+(?![\s|<])/, as "space not followed by another space or <". Thanks for your help!