DB<1> @aoa = ([qw / 1 2 3 4/], [qw/5 6 7/], [qw/8 9/]);

  DB<2>  x \@aoa
0  ARRAY(0x302ef588)
   0  ARRAY(0x3002a078)
      0  1
      1  2
      2  3
      3  4
   1  ARRAY(0x302ef878)
      0  5
      1  6
      2  7
   2  ARRAY(0x302ef8c8)
      0  8
      1  9

  DB<3> @result = map { $_->[0] } @aoa;

  DB<4> x \@result
0  ARRAY(0x302ef848)
   0  1
   1  5
   2  8

##</code><code>##

push @result,  $_->[0] for @aoa;