class UsefulClass {
    has $.a;
    has $.b;
    has $.c;

    method do-a { ... }
    method do-b { ... }
    method do-c { ... }

    # Str and Int can be converted to UsefulClass.
    multi method new (Str $s) { ... }
    multi method new (Int $s) { ... }
}

sub do-a-b-c (UsefulClass $cc) {
    $cc.do-a;
    $cc.do-b;
    $cc.do-c;
}

# I want to be able to write (1) instead of (2):
do-a-b-c "string";                   # (1)
do-a-b-c UsefulClass.new("string");  # (2)