sub split_array_in_two { ([splice @_, @_/2], \@_)[1,0] }
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or

sub split_array_in_two { my $l=@_/2; [@_[0..$l-1]], [@_[$l..$#_]] }
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or the funny recursive way:

sub da (\@\@\@) {
  my ($s, $a, $b)=@_;
  push(@$a, shift @$s), da(@$s, @$b, @$a) if @$s
}

my (@a, @b);
my @s=1..7;
da(@s, @a, @b);
print "@a - @b\n"
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