use strict;
my $str = '( [15] == @value 1@ || [15] == @value 2@ ) && ( [5] == @value 3 (ignore these)@ || [5] == @value 4@ ) || ( [2] == @value 5@ )';
my $regex = qr/\s*[()](?=(?:[^@]*@[^@]*@)*[^@]*$)\s*/mp;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html