[perl #129430] where-clause on capture does not work

[via RT]

# New Ticket Created by  Wenzel Peppmeyer 
# Please include the string:  [perl #129430]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=129430 >


sub f( |c where { c } ) {}; f 42

# OUTPUT«===SORRY!=== Error while compiling <tmp>␤Variable '&c' is not 
declared␤at <tmp>:1␤------> sub f( |c where { ⏏c } ) {}; f 42␤»

# expected to work analog to

sub f( *@a where { @a } ) {}; f 42