# while:
while $cond { $statements }
# ordinary funtion:
my_while $cond, { $statements };

# allowed in ordinary functions:
my_while $cond, █
# not allowed in builtin while:
while $cond █

##</code><code>##

rule statement_control:while {\
    <sym>
    [ <?before '(' [[my]? '$'\w+ '=']? '<' '$'?\w+ '>' ')'>   #'
        <.panic: "This appears to be Perl 5 code"> ]?
    <EXPR>                             {*}                      #= expr
    <pblock>                           {*}                      #= block
    {*}
}