use Scalar::Util qw( looks_like_number );
use List::Util qw( first );

my @menu = ( 'Known star', 'Create a new star', 'List Known Stars', 'Quit' );
my $input = '...';
my $picked;
if ( looks_like_number $input ) {
    $picked = $menu[ $input - 1 ];
}
else {
    $picked = first {
        length $input <= length $_
          and lc $input eq lc substr $_, 0, length $input;
    }
    @menu;
}
if ( !defined $picked ) {
    die "What do you mean by '$input'?";
}