my @a = (0,1,2,3);

foreach (@a) {print "'$_'\n";} # Prints each element.

print "\@a exists\n" if @a;

print "\@a is not Empty\n" if grep {defined($_)} @a;
    # Prints '@a is not empty' if any element in '@a' is defined.

my @b = (1, undef)
foreach (@b) {print "'$_'\n";}

print "\@b exists\n" if @b;

print "@b is not Empty\n" if grep {defined($_)} @b;