perl6 -e ' my %x = ( "a" => "A", "b" => "B", "c" => "C" );my $y="b"; %x<$y>="BB"; say %x;'
{$y => BB, a => A, b => B, c => C}


<code>
#!/usr/bin/env perl6

# This test is based on the following one liner that works
# perl6 -e ' my %x = ( "a" => "A", "b" => "B", "c" => "C" );my $y="b"; %x<$y>="BB"; say %x;'
# {$y => BB, a => A, b => B, c => C}


my $LineKey;
my $LineValue;

my %x = ( "a" => "", "b" => "", "c" => "" );
my @y=qw[ a=A b=B c=C ];
say @y;
say %x;

for @y -> $Line {
   $Line ~~ m/(.*?)("=")(.*)/;
   $LineKey=$0;
   $LineValue=$2;
   # say "LineKey = <$LineKey>  LineValue = <$LineValue>";

   for %x.kv -> $key, $value {
     # say "   key = <$key>   value = <$value>";
     if ( $LineKey eq $key ) {
        %x<$key> => $LineValue;
        say "LineKey = <$LineKey>   key = <$key>  LineValue = <$LineValue>  value = <$value>";
     }
   }
}

say %x;
</code>

HashLoopTest.pl6
[a=A b=B c=C]
{a => , b => , c => }
LineKey = <a>   key = <a>  LineValue = <A>  value = <>
LineKey = <b>   key = <b>  LineValue = <B>  value = <>
LineKey = <c>   key = <c>  LineValue = <C>  value = <>
{$key => ｢C｣, a => , b => , c => }