Regular Expressions 101

Positive Lookbehind(?<=start\s)

startthe literal text start (case sensitive)

\sany whitespace character

.*?any character (except for line terminators), repeated any number of times

Positive Lookahead(?=\s+(?:then|stop|other)|$)

1st Alternative\s+(?:then|stop|other)

\s+any whitespace character, repeated at least once

Non-Capturing Group(?:then|stop|other)

1st Alternativethen

thenthe literal text then (case sensitive)

2nd Alternativestop

stopthe literal text stop (case sensitive)

3rd Alternativeother

otherthe literal text other (case sensitive)

2nd Alternative$

$end of line

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.

25 tokens

Regular Expression

(?<=start\s).*?(?=\s+(?:then|stop|other)|$)

New

start a task then do something else
result = "a task"

start a task stop doing something else
result = "a task"

start a task then stop
result = "a task" 

start a task
a task

Substitution

start a task then do something else
result = "a task"

start a task stop doing something else
result = "a task"

start a task then stop
result = "a task" 

start a task
a task