SQL & PL/SQL :: Get Numeric Values From A Column Of Varchar Data?

I have a table and data like mentioned below.

create table emp( ename varchar2(20));
insert into emp values ('122');
insert into emp values ('abc');
insert into emp values ('0.2');
insert into emp values ('0-5');
insert into emp values ('25-30');

SQL> Select * from emp;
| ENAME |
-------------------
| 122 |
| abc |
| 0.2 |
| 0-5 |
| 25-30 |

I am running the code

SQL>select regexp_substr(ename , '^[[:digit:]]+.[[:digit:]]+$|^[[:digit:]]+$')
from emp;

AFTER RUNNING I AM GETTING THIS

| REGEXP_SUBSTR(ENAME,'^[[:DIGIT:]]+.[[:DIGIT:]]+$|^[[:DIGIT:]]+$') |
---------------------------------------------------------------------
| 122 |
| (null) |
| 0.2 |
| 0-5 |
| 25-30 |
| (null) |

Why it's not excluding '0-5' and '25-30', how I should write code to exclude this and Is there is any function in oracle to check for numeric in column and print.