Regular Expressions 101

^start of line

Group 1(\d+(?:\.\d+)*)

\d+a Unicode decimal digit, repeated at least once

Non-Capturing Group(?:\.\d+)*

*repeats the group contents below any number of times:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d+a Unicode decimal digit, repeated at least once

\.?optionally matches the literal . (46₁₀ / 56₈ / 2E₁₆)

\s+a Unicode whitespace character, repeated at least once

Group 2(.+)

.+any Unicode character (except for line terminators), repeated at least once

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^(\d+(?:\.\d+)*)\.?\s+(.+)

1.     Header 1
1.2.  SubHeader2
1.2.1     Subheader 
1.2.2.   Another header
1.2.2.1        Test
1.2.2.2.    Test2