No attempt a golf, but clear I think. 

#! perl -sw
use strict;

while (<DATA>) {
    chomp;
    print sprintf('%-20s', $_),
        (/^[a-z][a-z-]+?[a-z]$/i and not /--/)
        ? ' is '
        : ' is not ',
        'a valid word according to the rules specified.', $/;
}

__DATA__
brian0
brian-
-brian
bri--an
Bria-n
br-i-an
brian

[download]

P.S. There's no need to put the whole question in the title:)

Nah! You're thinking of Simon Templar, originally played (on UKTV) by Roger Moore and later by Ian Ogilvy

In reply to Re: Sorting words, keeping only words that start with a letter and contain only letter characters, and hypens, and end in a letter by BrowserUk
in thread Sorting words, keeping only certain words by Anonymous Monk

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