for my $count (0..4) {
    print("$count: ");
    if    ($count < 1) { print "None\n";   }
    elsif ($count < 2) { print "Unique\n"; } 
    else               { print "$count\n"; }
}

##</code><code>##

0: None
1: Unique
2: 2
3: 3
4: 4

##</code><code>##

my $substr = 'xxx';
for my $parent (
   'fred bill xx joe',
   'fred bill xxx joe',
) {
    my $count = () = $parent =~ /\Q$substr/;
    if    ($count < 1) { print "None\n";   }
    elsif ($count < 2) { print "Unique\n"; } 
    else               { print "$count\n"; }
}

##</code><code>##

None
Unique