You should post your program. Take care of "modifiers" (http://perldoc.perl.org/perlre.html#Modifiers) :

while (<DATA>) {
    /([A-Z]+)/i;  # upper AND lower!
    print $1,"\n";
}
[download]

output :

ABU
individual
AFGHAN
AYAT
a
Pushtoon
Sabaqah