sub my_uc {
    my $c = shift;
    return uc($c);
}

my @a = ('a'..'c');

@a = map { uc($_) } @a;
print "==>@a<== { uc(\$_) }\n";

@a = map { my_uc($_) } @a;
print "==>@a<== { my_uc(\$_) }\n";

@a = map uc, @a;
print "==>@a<== uc,\n";

@a = map my_uc, @a;
print "==>@a<== my_uc,\n";