In your special case you can do without a regex and instead use substr and length: 
while (<DATA>) {
    chomp;
    print if substr($_,0,1) eq 'R' && length == 3;
}
 
__DATA__
raa
Raa
Raab

[download]

Update: Rereading your question, my solution only applies if you read 'letter' as 'any character'.

-- Hofmator

In reply to Re: Wildcard? by Hofmator
in thread Wildcard? by bobothesmart

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