my @nloops = join(',',@{$collection[0]}); and try
print @nloops[1] OUT

[1,1,1,1,1]
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but the correct should be

1

Actually, there is nothing in @nloops[1]. It's not defined. join returns a scalar. Setting a scalar to @nloops places the scalar in $nloop[0].

What you probably wanted to do is:

my @nloops = @{ $collection[0] };
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Now @nloops contains a list of values. $nloops[0] now contains 1.