grep in array -perl

hi all
i have 2 array one is refernce array where as other array is generated from text file. array A has all letters from A-z and a-z and i want to find out which letters are missing in generated array and push them in another array to display them.
i have following code ....

for my $ref (@reference) { #this is reference array 
    if ( ! grep $ref, @no ) # @no is generated array 
    {
        push @usable, $ref ; # @usable array to store unused letters 
    }
}

this code prints no usable letters even when there are ...can u tell where i m doing wrong ?

Looks like the grep is specified incorrectly.

Look at this:

# perl -e 'for $ref ('A'..'Z') { if (!grep(/^${ref}$/, 'E'..'Z')) { print $ref, "\n" } }'
A
B
C
D