local ($, , $\) = (', ', "\n"); # for print
my @a = (1..10);
print @a;
--$_ foreach @a;
print @a;
map { $_ *= 2 } @a;
print @a;
print grep { $_ *= $_ } @a;
print @a;

1, 2, 3, 4, 5, 6, 7, 8, 9, 10
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
0, 2, 4, 6, 8, 10, 12, 14, 16, 18
4, 16, 36, 64, 100, 144, 196, 256, 324
0, 4, 16, 36, 64, 100, 144, 196, 256, 324