UltraEdit, UltraCompare, UEStudio forums

Or you can use this in case there are more adjacent capital letters :) F: (?-i)(?<![A-Z\s])([A-Z]+) R: <space>\1 BTW a little off-topic - UltraEdit version 26.00 uses Boost Perl regular expression library version 1.68 . And IDM implemented almost all missing features (backtracking control verbs, nam...

It is also possible to use (?<! \s ) ( [A-Z] ) and replace string being a space and $1 or \1 and option Match case is checked which is very important as otherwise [A-Z] is equal [A-Za-z] . The lookbehind before the capturing group prevents inserting a space on character left to upper case ASCII lett...

1. Find what: ([[:upper:]]) or  (?-i)([A-Z]) or (?-i)(\p{Lu}) Replace with:  $1 (There is space before $) 2. Find what: [[:upper:]][[:lower:]]* or               (?-i)\p{Lu}\p{Ll}* or               (?-i)[A-Z][a-z]* See also Perl Regular Expression Syntax .