You could overload the has method (which is actually in Set::Scalar::Base), or just add something similar to it like so

use Set::Scalar;

sub Set::Scalar::Base::has_re {
    my $self = shift;

    my @has;
    foreach my $el (keys %{$self->{'elements'}}) {
        push @has, $el =~ /$_/ for @_;
    }

    return wantarray ? @has : "@has";
}

my $s = Set::Scalar->new('a','b','c(d)');

if(my $sub_el = $s->has_re(qr/c\((.+)\)/)) {
    print "found it $sub_el\n";
}

__output__

found it d
[download]

That's not the greatest example of well-tested code but I'm sure you get the idea. Also make sure you quote your regexes or you won't get what you expect (the qr// operator is your friend!).
HTH

_________
broquaint