As discussed here, it would be great to have the ability to match only partial words with the on HOTLINK event:

Some clarifications:

I thought that getting the character directly under the mouse cursor would solve your issue, you would check if that's equal to 'e' and if so make it hotlinks...
However that doesn't work for all situations: for example if you wanted to hotlink if you are on the last 't' of "test", checking the letter under the cursor would fail, you would need to check the letter + the position of the letter in the word.

Something like $hotlink(mouse) returning the letter under the cursor and $hotlink(mouse).pos to get the position of the letter in the matched word.