use List::Util qw( sum );
use List::MoreUtils qw( zip );

my $str = "aabceezazerrfde";
my $wanted = "aez";
my @values = (7,2,26);

my @wanted = split //, $wanted;
my %value_of = zip @wanted, @values;
my $tot = sum map { $value_of{$_} || 0 } split //, $str;