nothing fancy:

#!/usr/bin/perl

my @array = ( a .. x, undef );
print "@array\n";

my (@a,@b);
for ( 0 .. $#array ) {
  if ( $_ % 2 ) { 
    push @b, $array[$_];
  } else {
    push @a, $array[$_];
  }
}

print "a: '@a'\n";
print "b: '@b'\n";
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qq