Do you mean something like this?

#!/usr/bin/perl
use warnings;
use strict;

my @ar = (qw/a b c/, [ 'level 1', 'level 1b',
                         [ 'level 2', 'level 2b',
                             [ 'level 3', [ 'level 4', [[ 'level 6 ']]
+ ]]]]);

sub flatten {
    return map ref $_ ? flatten(@$_) : $_, @_;
}

print join ', ', flatten @ar;
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