rx:P5 not implemented

[jaffa4]

if "a"~~ rx:P5/a/
{
say "match";

}

does not compile or run..

Unhandled exception: Autoloading NYI
at D:\src\niecza\niecza\boot\lib\CORE.setting line 1366 (die @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 4809 (Regex.tweak @ 6)
at D:\src\niecza\niecza\src\STD.pm6 line 523 (ANON @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 526 (STD.babble @ 7)
at D:\src\niecza\niecza\src\STD.pm6 line 577 (STD.quibble @ 4)
at D:\src\niecza\niecza\src\STD.pm6 line 2668 (P6.quote:rx @ 5)
at D:\src\niecza\niecza\src\STD.pm6 line 0 (STD.quote @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 2501 (P6.value:quote @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 0 (STD.value @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 2073 (P6.term:value @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 0 (STD.term @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 2049 (P6.termish @ 15)
at D:\src\niecza\niecza\src\STD.pm6 line 4665 (ANON @ 5)
at D:\src\niecza\niecza\src\STD.pm6 line 4778 (STD.EXPR @ 13)
at D:\src\niecza\niecza\src\STD.pm6 line 1255 (P6.xblock @ 8)
at D:\src\niecza\niecza\src\STD.pm6 line 1494 (P6.statement_control:if @ 5)
at D:\src\niecza\niecza\src\STD.pm6 line 0 (STD.statement_control @ 3)
at D:\src\niecza\niecza\src\STD.pm6 line 1406 (P6.statement @ 11)
at D:\src\niecza\niecza\src\STD.pm6 line 1329 (P6.statementlist @ 16)
at D:\src\niecza\niecza\src\STD.pm6 line 1185 (P6.comp_unit @ 9)
at D:\src\niecza\niecza\src\STD.pm6 line 109 (STD.TOP @ 8)
at D:\src\niecza\niecza\boot\lib\CORE.setting line 2813 (Grammar.parse @ 4)
at D:\src\niecza\niecza\src\NieczaFrontendSTD.pm6 line 291 (NieczaFrontendSTD.parse @ 29)
at D:\src\niecza\niecza\src\NieczaCompiler.pm6 line 35 (NieczaCompiler.compile @ 7)
at D:\src\niecza\niecza\src\NieczaCompiler.pm6 line 62 (NieczaCompiler.compile_file @ 6)
at D:\src\niecza\niecza\src\niecza line 166 (mainline @ 77)
at D:\src\niecza\niecza\boot\lib\CORE.setting line 3842 (ANON @ 3)
at D:\src\niecza\niecza\boot\lib\CORE.setting line 3843 (module-CORE @ 65)
at D:\src\niecza\niecza\boot\lib\CORE.setting line 3843 (mainline @ 2)
at line 0 (ExitRunloop @ 0)

[colomon]

This is a well-establish Not Yet Implemented feature.