I've been using the following, but it's obviously not as elegant as tee. I need to dig into tee's guts and find out how it does what it does.

topen('STDOUT','>file1.txt','>>file2.txt');
tprint("text\n");
tprint("text\n");
tclose();

BEGIN {
    my (@tp_h, $tp_s);
    sub topen {
        tclose();
        for (@_) {
            if ($_ eq 'STDOUT') { $tp_s = 1; next; }
            open($_, $_) || die $!;
            push @tp_h, $_;
        }
    }
    sub tclose {
        close $_ for @tp_h;
        @tp_h = (); $tp_s = 0;
    }
    sub tprint {
        print @_ if $tp_s;
        print $_ @_ for @tp_h;
    }
}
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