Not only ugly, it doesn't match the OP's spec. It matches everything from the first non-special character through the last comma. Try it with

$foo = 'var-a numeric (10,0) = NULL, var-b char (10) = NULL, var-c dum
+my (1, 5)';
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Since you're specifying a capture group, you're probably better trying for a m//g style capture, rather than using split. Like so:

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;
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