Looks like it's just a constraint issue.

import std.regex;

void main() {
    enum re = ctRegex!".";
    auto str = "a.b";
    std.regex.splitter(str, re);
}

test.d(6): Error: template std.regex.splitter(Range,RegEx) if (is(BasicElementOf!(Range) : dchar) && is(RegEx == Regex!(BasicElementOf!(Range)))) does not match any function template declaration
test.d(6): Error: template std.regex.splitter(Range,RegEx) if (is(BasicElementOf!(Range) : dchar) && is(RegEx == Regex!(BasicElementOf!(Range)))) cannot deduce template function from argument types !()(string,StaticRegex!(char))