%{ $href } # better than %$href
@{ $aref } # better than @$aref

##</code><code>##

if ( scalar @{ $lib || [] } ) {
    ...
}

##</code><code>##

$ perl -Mstrict -E 'my $aref = [ "", undef ]; say scalar @{ $aref || [] } ? "True" : "False";'
True

##</code><code>##

$ perl -Mstrict -E 'my $aref = [ "", undef ]; say scalar ( grep { length $_ } @{ $aref || [] } ) ? "True" : "False";'
False