Comment 25 for bug 465309

No. ^. is not equivalent. ^. means to match the first character on the line, and if doing a replace then the first character would be deleted. ^ by itself matches the start of the line (not including any characters), and replacing it with something effectively inserts the "replacement" text at the start of the line. You could use something ugly like replacing ^(.) with ${1}PREFIX to avoid deleting the first character, but that would fail on blank lines which don't have any characters in them.

In any case, ^ (by itslef) is a standard, well-defined regular expression syntax used everywhere else (Perl, Python, vim etc. etc.) and Libre Office should not do something incompatible.