Regular Expressions 101

Explanation

Pro

1st Alternative(?s)(?:START).*?(?:END)(?-s)

(?s)applies the following effective flags to the remainder of the pattern: gms

s modifier: single line. Allows a dot to match line terminators

Non-Capturing Group(?:START)

STARTthe literal text START (case sensitive)

.*?any character, repeated any number of times

Non-Capturing Group(?:END)

ENDthe literal text END (case sensitive)

(?-s)applies the following effective flags to the remainder of the pattern: gm

s modifier: -single line. A dot does not match line terminators

2nd Alternative//.+

//the literal text //

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

3rd Alternative\. old

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

oldthe literal text old (case sensitive)

4th Alternative^\s+old(*SKIP)(*FAIL)

^start of line

\s+any whitespace character, repeated at least once

oldthe literal text old (case sensitive)

(*SKIP)acts like (*PRUNE), but the next unanchored match attempt starts where (*SKIP) was reached instead of at the next subject character

(*FAIL)forces the current match attempt to fail at this position

5th Alternative\b(old)\b

\ban ASCII word boundary

Group 1(old)

oldthe literal text old (case sensitive)

\ban ASCII word boundary

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

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

25 tokens

Regular Expression

(?s)(?:START).*?(?:END)(?-s)|//.+|\. old|^\s+old(*SKIP)(*FAIL)|\b(old)\b

xx START xx old xx END xx   --> ignore
xx old xx                   --> REPLACE !
START xx old                --> ignore
      xx old xx END         --> ignore
      xx old xx             --> REPLACE !
// xx old                   --> ignore
xx // xx old                --> ignore
xx . old old xx             --> ignore first one, replace second one
.
  old                       --> ignore
  (old) xx                  --> REPLACE !
xx old xx                   --> REPLACE !

Substitution

xx START xx old xx END xx   --> ignore
xx old xx                   --> REPLACE !
START xx old                --> ignore
      xx old xx END         --> ignore
      xx old xx             --> REPLACE !
// xx old                   --> ignore
xx // xx old                --> ignore
xx . old old xx             --> ignore first one, replace second one
.
  old                       --> ignore
  (old) xx                  --> REPLACE !
xx old xx                   --> REPLACE !