You're exactly right in your analysis of what is going on and I'd consider that a serious bug in the documentation of the module. It actually gets worse when you see the rest of that code sample:

my @choices = [ qw/one one.green one.blue one.yellow two.blue
                   two.green two.cyan three.red three.white 
                   three.yellow/ ];

$mw->Button->pack(-side => 'left');

my $me = $mw->MatchEntry(
        -choices        => @choices,
        -fixedwidth     => 1, 
        -ignorecase     => 1,
        -maxheight      => 5,
        -entercmd       => sub { print "callback: -entercmd\n"; }, 
        -onecmd         => sub { print "callback: -onecmd  \n"; }, 
        -tabcmd         => sub { print "callback: -tabcmd  \n"; }, 
        -zerocmd        => sub { print "callback: -zerocmd \n"; },
    )->pack(-side => 'left', -padx => 50);
[download]

Now consider what happens if @choices contains more than one element (as you'd expect to be able to do with an array). It gets particularly bad if the array has an even number of elements - all of the following parameters will be broken.

I recommend you raise a bug on rt.cpan.org and, in the meantime, make a note of the problem on AnnoCPAN.