DB<100> use List::MoreUtils "pairwise"

  DB<101> @vars=qw(X Y)
 => ("X", "Y")

  DB<102> @appends=qw(x y)
 => ("x", "y")

  DB<103> pairwise { $a .= $b } @vars, @appends
 => ("Xx", "Yy")

  DB<104> @vars
 => ("Xx", "Yy")

##</code><code>##

  DB<105> @vars=qw(X Y)
 => ("X", "Y")

  DB<106> @vars = pairwise { $a . $b } @vars, @appends
 => ("Xx", "Yy")