Those are acronyms, not abbreviations. And, acronyms tend to be all uppercase and also tend to not be words (though there are some very obvious exceptions, especially with acronyms that are chosen to be words.)

Good luck.

You need a list of valid abbreviations and acronyms.

something like Lingua::EN::Sentence might be a good start (but it only has a tiny list of acronymns/abbreviations)

Joost.

[http://ftp.gnu.org/pub/gnu/vera/vera-1.9.tar.gz|vera] is a text database of acronyms available at [http://www.gnu.org|gnu.org]. It would be pretty easy to take the initial character of your candidate acronym, lowercase it and search the vera.? file for a match.

my $meaning;
if ( /\b([A-Z]?)\b/ ) {
    open my $fh, '<', '/path/to/vera/vera.' . lc( substr $1, 0, 1)
        or die $!;
    while (<$fh>) {
        $meaning = <$fh> and last if /$1/;
    }
}

If you want to do a lot of that, it would probably pay to set up a simple database of the vera data. Perl can do that for you, too.

The problem with any/all solutions to this problem is that of acceptable usage. For example, there are technical documents who would refer to SCUBA but travel brochures that would refer to scuba. Similarly scientists work with LASER but companies sell laser devices.

You cant create rules about pronouncability because both 'laser' and 'scuba' are pronouncable. 'Sky' contains no vowels and so might/might not be an acronym. Qantas contains no 'u' after the Q, nor does Iraq. Qantas is the "Queensland and Northern Territory Aerial Service" however, noone uses that outside of a trivia game these days. Its considered a word. Iraq, of course, is from another language and doesn't follow English rules.

Databases like vera can help you with a list of known acronyms but in Real Estate advertising 'LUG' is a lock-up-garage whereas in a mechanical journal a 'lug' is a type of nut.

Given all this, when parsing user text I normally require that there be one or more lower-case letters in users input. That way I know they didn't just type it with the Caps-Lock button on. If it's all in capitals I'll ask them to change or confirm what they've entered.

Afaik the correct definition is given by Halley, the letters must form a word. Merely being pronounced like a word, for example SCSI isn't sufficient. There are also 'contracions' which are one step short of abbreviations, for example COINTEL. Technical English says an abbreviation should be written with periods as separators, for example I.B.M. or with an appended period as in Mr. and Ms.
The only answer to catching and mapping all these shortened forms is a database/list of some kind. The Oxford dictionary used to have several pages devoted to them, but I think these days there are so many from specialised fields that no-one bothers to compile them anymore. btw Lug, also = Linux User Group and an kind of knot. My most hated confusing acronym is LOD in games design which is 'level of detail' and 'last object drawn' in the engine and 'land object down' in terrain building.