G'day rem45acp,

Here's another way to do it (I've added a few more tests to ones you posted):

#!/usr/bin/env perl -l

use strict;
use warnings;

my @tests = qw{
    one one.two one.two.three four.five.six.seven one. one-two
    .one .one. . .. .@. one.good.egg one.-bad-.egg
};
print "'$_': ", grep(! /^\w+$/, split /\./, $_, -1) ? 'bad' : 'good' f
+or @tests;
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Output:

'one': good
'one.two': good
'one.two.three': good
'four.five.six.seven': good
'one.': bad
'one-two': bad
'.one': bad
'.one.': bad
'.': bad
'..': bad
'.@.': bad
'one.good.egg': good
'one.-bad-.egg': bad
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[See split if you're unfamiliar with the 3-argument form.]