# Regex character class

## Function

Explain how to write character classes and range matching.

## Syntax

```bt
regex(pattern, flags)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| pattern | String | No | '' | Can contain character classes such as [abc], [a-z], [^0-9], etc. |
| flags | String | No | '' | Regular flags. |

## Return value

| Type | Description |
| ------ | ------ |
| Regex | Returns a Regex object. |

## Example

```bt
rule = regex('^[a-z]+$', 'i')
result = rule.test('BT')

// Output: true
print result
```

## Notes

- Whether the character range is case-sensitive or not is determined by the i flag.