I'd normally use a slightly simpler version of JohnGG's splice approach. Something like

my @arr = qw/1 2 3 4 5 6 7 8/;
while(my ($x,$y) = splice @arr,0,2) {
  say "$x => $y";
}
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Something I've needed in the past was to get two arrays (odds and evens). Grep can do this. You could combine them into a hash thus:

my @arr = qw/1 2 3 4 5 6 7 8/;

my ($j,$i)=(0,0);
my ($x,$y) = ([grep { ++$i % 2} @arr] , [grep {$j++ % 2} @arr]);
my %hash;
@hash{@{$x}}=@{$y};

for(keys %hash) {
  say "$_ => $hash{$_}"
}
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1 => 2
3 => 4
7 => 8
5 => 6
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my @arr = qw/1 2 3 4 5 6 7 8/;
push @arr, undef;
push @arr, 9;


my ($j,$i)=(0,0);
my ($x,$y) = ([grep { ++$i % 2} @arr] , [grep {$j++ % 2} @arr]);
$i=0;
for(@{$x}){
  say $_ ." => " . $y->[$i++] if($_);
}
[download]