Just because I've never seen 'reductions' used before :)

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11162727
use warnings;
use List::Util qw( reductions );
use Data::Dump 'dd';

dd map s/.*\K,/ and/r, reductions { "$a, $b" } 'A'..'Z';
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Outputs:

(
  "A",
  "A and B",
  "A, B and C",
  "A, B, C and D",
  "A, B, C, D and E",
  "A, B, C, D, E and F",
  "A, B, C, D, E, F and G",
  "A, B, C, D, E, F, G and H",
  "A, B, C, D, E, F, G, H and I",
  "A, B, C, D, E, F, G, H, I and J",
  "A, B, C, D, E, F, G, H, I, J and K",
  "A, B, C, D, E, F, G, H, I, J, K and L",
  "A, B, C, D, E, F, G, H, I, J, K, L and M",
  "A, B, C, D, E, F, G, H, I, J, K, L, M and N",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N and O",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O and P",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P and Q",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q and R",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R and S",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S and T",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T and U",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U and V
+",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V an
+d W",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W
+ and X",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W
+, X and Y",
  "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W
+, X, Y and Z",
)
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