sub my_new_uc {
    my $c = shift // $_;
    return uc($c);
}

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

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

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

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

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