This seems to work:

use strict;

my @array = qw/A B C [ D ] E F/;
my @outarray;

my $outid = 0;
my $incrm = 1;
for my $ch ( @array ) {
    $outarray[$outid] .= $ch;
    $incrm = ( $ch eq '[' ) ? 0 : ( $ch eq ']' ) ? 1 : $incrm;
    $outid += $incrm;
}
print "@outarray\n";
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