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use List::MoreUtils qw(zip);

...
my $string = join '', zip @arrToJoin, @{[ @arrOfJoiners, '' ]};

print "$string\n";

use List::MoreUtils qw(zip);

...
push @arrOfJoiners, ('') x ( @arrToJoin - @arrOfJoiners );
my $string = join '', zip @arrToJoin, @arrOfJoiners;
print "$string\n";