For instance, suppose you want to strip out certain HTML tags from a document, say (just for the sake of the argument) <span style="...">. How would you do it if neither "<span style=".*?">" nor "<span style="[^"]">" nor any variation thereof are correctly interpreted by the editor's regex engine? Sheesh.
I'm not expecting Perl 5 match-time code evaluation or other such things, but non-greedy stars and negated character classes are pretty basic features.