# this matches each character once
$filecontents =~ m/./g;

# this version also puts a copy of each match into @characters
my @characters = $filecontents =~ m/./g;

# this counts the number of elements in @characters
my $CharCount = scalar @characters;

# to verify your regex is matching correctly
# this will print a list of each item counted:
for (@characters){
    print "$_ \n";
}