Code:
my @a = ( a1, a2, a3, a4, a5, );

map(&process, @a);
print join " ",@a;

sub process {
push(@a,"x");;
unshift(@a,"y");;
print "array has " . scalar @a . " elements. This one is " ."====$_\n";
}

Output:
array has 7 elements. This one is ====a1
array has 9 elements. This one is ====a2
array has 11 elements. This one is ====a3
array has 13 elements. This one is ====a4
array has 15 elements. This one is ====a5
y y y y y a1 a2 a3 a4 a5 x x x x x