Besides the map solutions already posted, here's two others:
setup for both:

use Data::Dumper;
my @bigarray = (
    [ "123*jeff", "tortoise", "qwerty" ],
    [ "456*john", "parrot", "azerty" ],
    [ "789*jane", "budgie", "abcdef" ],
    );
print Dumper \@bigarray;  # before
...
print Dumper \@bigarray;  # after
[download]

• Using splice:

  splice @$_, 0, 1, split /\*/, $_->[0] for @bigarray;
  [download]

• Using shift and unshift:

  foreach my $arr ( @bigarray ){
    my $item = shift @$arr;
    unshift @$arr, split /\*/, $item;
  }
  [download]

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