goal

# subroutine solution:
my $*GOAL;

sub g($in = 'o') {
    $*GOAL = $*GOAL ?? $*GOAL ~ $in !! 'g' ~ $in;
    if $in eq 'al' {
        $*GOAL ~= "\n";
        return $*GOAL = $*GOAL but False
    }
    &?ROUTINE # return the current subroutine
}

print g('al');
print g()('al');
print g()()()()('al');


# role solution (if "i need the sigil" doesn't disqualify it):
role o-role {
    multi method postcircumfix:<( )>($o) {
        return (self ~ 'o') does o-role;
    }
    multi method postcircumfix:<( )>($o where $o eq 'al') {
        return (self ~ "al\n");
    }
}

role g-role {
    method postcircumfix:<( )>($g = '') {
        return ('g' does o-role)($g);
    }
}

my $g = 'g' does g-role;

print $g('al');
print $g()()()('al');
#     ^- this sigil can't go away :(