my $string = "an apple in the fridge";
my @regexes = ("an apple", "apple in a fridge", qr/(?:pine)?apples/);
my %matches;
for my $regex (@regexes) {
    my @matches = $string =~ /$regex/;
    for my $match (@matches) {
        $matches{$match} = 1; # or increment to keep score
    }
}
my @matches_sorted_by_length = sort {length($a) <=> length($b)} keys %matches;
print "Longest match is $matches_sorted_by_length[-1]\n";