my $str = 'var-a numeric (10,0) = NULL, var-b char (10) = NULL, var-c dummy (1, 5)';
my @bits = $str =~
 /(?:^|,)    # Match starting at beginning of string or a comma
  (      # Capture
   (?:      # group of
    [^(,]   #  non-parens 
    |       #  or
    \(.*?\) #  open-paren to close-paren
   )*       # as many times as possible
  )/gx;
print ">$_<\n" for @bits;