$ perl -MMojo::DOM -E 'my $dom = Mojo::DOM::->new("<p></p>"); my $x = $dom->at("p.missing")->text(); say defined $x ? "not missing" : "really missing"'
Can't call method "text" on an undefined value at -e line 1.

##</code><code>##

$ perl -MMojo::DOM -E 'my $dom = Mojo::DOM::->new("<p></p>"); my $x = $dom->at("p.missing"); say defined $x ? "not missing" : "really missing"'
really missing

##</code><code>##

$ perl -MMojo::DOM -E 'my $dom = Mojo::DOM::->new(q{<p class="missing"></p>"}); my $x = $dom->at("p.missing"); say defined $x ? "not missing" : "really missing"'
not missing