What are inline modifiers in regular expressions and how to use them

Inline modifiers are very similar to flags, but we can include them directly within a regular expression.

That is to say, unlike global modifiers that apply to the entire expression, inline modifiers allow us to modify the behavior of the expression only in the part where they are inserted.

Syntax of inline modifiers

Inline modifiers are specified using the syntax (?mod), where mod is the modifier we want to apply.

The most common inline modifiers include:

Modifier i (Case Insensitive)

The i modifier is useful when we want the match to be case insensitive.

In this example, we use (?i) to allow “hello” to match regardless of its capitalization.

Modifier m (Multi-line)

The m modifier allows the anchors ^ and $ to work on each line of text.

Here, (?m) allows ^ to match the start of “Second” in the second line of the text.

Modifier s (Dot All)

The s modifier allows the dot (.) to match newline characters.

Here, (?s) makes .* match the newline between “Hello,” and “how are you?“.

Modifier x (Verbose)

The x modifier allows including spaces and comments in the expression, improving its readability.

With (?x), we can include comments in the expression to make it more understandable.

Combining inline modifiers

We can combine several inline modifiers in a single expression. To do this, we simply have to join the modifiers in our (?mod).

For example, if we want a match that

• Is case insensitive (?i)
• Works across multiple lines (?m)

We can do this by combining both modifiers like this (?im)