I have orverriden the default word delimiters for latex
(which by the way, should be changed).
This worked fine in v5.1.1, but not in v5.4.
In v5.4, while incremental search respects my word delimiters,
ordinary search and search and replace does not.
For example, I added the character "_" to the word delimiter list.
When I do a search for the pattern "<x>" in the text "x_1",
it does not fine "x".