sub multidecode_utf8 {
    my $s = shift;
    1 while $s =~ tr/\x80-\xFF// && utf8::decode($s);
    return $s;
}
[download]

Tested with:

use strict;
use warnings;

use Test::More tests => 12;

for my $orig (
    "abc",
    "\xC9ric",
    "\x{2660}\x{2661}\x{2662}\x{2663}",
) {
    my $str = $orig;
    for (0..3) {
        is multidecode_utf8($str), $orig;
        utf8::encode($str);
    }
}
[download]