Regular expressions are now (as of Version 8) fully supported in BSV searches. To specify that your search string is to be interpreted as a regular expression, tick the "Regular expression" checkbox on the Find text, Replace text, LFIND, or LCHANGE dialogs.
Note that:
When searching for multi-word strings, replace each space with \s+ (meaning "one or more white space characters"). "White space characters" include spaces, tabs, carriage returns, and newlines.
Regular expressions are very powerful and also very dangerous. Never hit "replace all" without thoroughly testing your expression first. The best plan is to test each new expression on dummy files. Step through each change interactively, making sure that no unexpected results occur.
One of the biggest dangers with regular expressions is that of the "greedy" search. If I want to find each trademark in a file, I might create an expression like <tm\s+[\s\S]+</tm>. This says: "Start with the literal string <tm, then one or more white space characters, then any character at all, repeated until I get to the literal string </tm>". But what if there are many trademarks in the file? The selected text will start at the first "<tm" and end at the last "</tm>"! This is a greedy search.
The correct expression is in the second example above: <tm\s+[\s\S]+?</tm> . Notice the ?, which means "return the smallest possible string that matches the specification". This is a non-greedy search.