You could use a canned /regexp?/i as follows: 
use strict;
use warnings;
use Regexp::Common qw(balanced);

my @streams = (
               '(aaa) (bbb (ccc( ddd) eee)) (fff)',
               '  (a) ((bc (d))  ef) h',
               '(a)',
               '(a) ',
               '(a)   (bc)',
               '',
               );

my $PATTERN = $RE{balanced}{-keep};

for my $input (@streams) {
    print qq("$input" => );
    my @pieces = ($input =~ /$PATTERN/g);
    printf qq(%s\n), join qq( ), map {qq("$_")} @pieces;
}

[download]
which prints: 
"(aaa) (bbb (ccc( ddd) eee)) (fff)" => "(aaa)" "(bbb (ccc( ddd) eee))"
+ "(fff)"
"  (a) ((bc (d))  ef) h" => "(a)" "((bc (d))  ef)"
"(a)" => "(a)"
"(a) " => "(a)"
"(a)   (bc)" => "(a)" "(bc)"
"" =>

[download]
This assumes that you had a typo in your post and you actually want balanced parens. Cheers.

In reply to Re: regex to parse (nested) parenthesis delimited string? by fenLisesi
in thread regex to parse (nested) parenthesis delimited string? by varian

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