Another way to do it is to store your wanted values in a hash and split your string into an array, as follows:

#!/usr/bin/env perl

use warnings;
use strict;
my $str = 'aabceezazerrfde';
my %vals = (
    'a' => 7,
    'e' => 2,
    'z' => 26
);
my @chars = split //, $str;
my $tot = 0;
for (@chars) {
    if (exists $vals{$_}) {$tot += $vals{$_}}
}
print "total = $tot\n";
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