I would avoid both of those approaches. The first involves too much repetition of code, and the second is too obfuscated. How about like this:

my ( $src, $dst ) = ( $opt_reverse ) ? ( 0, 1 ) : ( 1, 0 );

if ( $opt_ignore ) {
    $map{lc($array[$dst])} = $array[$src];
} else {
    $map{$array[$dst]} = $array[$src];
}
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(I hope I got the polarity right on what "reverse" means, but in any case, I think you can see the point.)

(update: got rid of the "defined()" call -- the option values should just be true or false, and undefined is false)

Another update: better solution:

my ( $src, $dst ) = ( $opt_reverse ) ? (0,1) : (1,0);
my $key = ( $opt_ignore ) ? lc($array[$dst]) : $array[$dst];

$map{$key} = $array[$src];
[download]