\b at the beginning of the pattern means "start matching at a word
boundary".
.. matches any single character
..{0,1500} means "match as many characters as you can but not more than
1500 of them"
(?: ) means "group this subpattern as if it was in ( ), but don't save
whatever it matches
\W matches any "non-word" character (e.g. anything but 0-9,A-Z,a-z_)
| means "or"
$ means the end of the string.
So given a string like this "Hello world lots and lots of words....."
the pattern will start with the boundary at the beginning of "Hello" and
match up to 1500 characters, stopping at the end of the string or at the
last non-word character before the 1501st character, whichever comes
first. If oRE.Global is true, successive matches will start where the
previous match ended.
