use strict;
use Data::Dumper;

my %hash;

$_="ABCD----[this]  fgab [that]  BFTE-- [other] AB CD   EF---- [foo]  FOO[this][that][other] BAR []";

while ( /\G\s*([\w ]+)[\s-]*\[([\w\[\]]*)\]/g )
{
  $hash{$1}=$2;
  $hash{$1} =~ s/\]\[//g;
}

print Dumper (\%hash);

#$VAR1 = {
#          'BAR ' => '',
#          'fgab ' => 'that',
#          'ABCD' => 'this',
#          'BFTE' => 'other',
#          'FOO' => 'thisthatother',
#          'AB CD   EF' => 'foo'
#        };