Programming :: Counting To A Specific Character?

I am loading variables for cXtXdXsX disk names into a script, and at present I have only accounted for there being 3 characters from c to t. I need to change it to a variable recognition so that it can count any number of charcters such as c1t , c10t , or c100t.

I can then take that information and use it with the following string to strip off the lead characters so as to make the 3 in $substr either a variable or redirect to multiple occurrences of raw based on the count returned.

sub raw {
$substr = substr ($_, 3);
$raw1 = substr ($substr, 0, -4);
$raw = lc($raw1);
}

how to count from the c to the t inclusive so I get 3, 4, 5, etc ...