regex101: PCRE (Legacy) Match Workspace

Group strike_all(?<strike_all> # strikethrough can be multilines (?<!\\)\~{2} # Start with 2 tilde (?!\n) # but not followed by a new line to avoid any previous tildes getting caught (?<strike_content> # the content which excludes any tilde unless they are escaped (?>\\[\~]|[^\~])*+ ) (?<!\\)\~{2} # terminated by 2 tildes )

Comment: strikethrough can be multilines

Negative Lookbehind(?<!\\)

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

\~{2}the literal ~ (126₁₀ / 176₈ / 7E₁₆) , repeated exactly 2 times

Comment: Start with 2 tilde

Negative Lookahead(?!\n)

\na line-feed (newline) character (ASCII 10)

Comment: but not followed by a new line to avoid any previous tildes getting caught

Group strike_content(?<strike_content> # the content which excludes any tilde unless they are escaped (?>\\[\~]|[^\~])*+ )

Comment: the content which excludes any tilde unless they are escaped

Atomic Group(?>\\[\~]|[^\~])*+

*+repeats the group contents below any number of times:

1st Alternative\\[\~]

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

Character Class[\~]

\~the literal ~ (126₁₀ / 176₈ / 7E₁₆)

2nd Alternative[^\~]

Negated Character Class[^\~]

\~the literal ~ (126₁₀ / 176₈ / 7E₁₆)

Negative Lookbehind(?<!\\)

\\the literal \ (92₁₀ / 134₈ / 5C₁₆)

\~{2}the literal ~ (126₁₀ / 176₈ / 7E₁₆) , repeated exactly 2 times

Comment: terminated by 2 tildes

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

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

25 tokens

Regular Expression

(?<strike_all>                  # strikethrough can be multilines
    (?<!\\)\~{2}                # Start with 2 tilde
    (?!\n)                      # but not followed by a new line to avoid any previous tildes getting caught
    (?<strike_content>          # the content which excludes any tilde unless they are escaped
        (?>\\[\~]|[^\~])*+
    )
    (?<!\\)\~{2}                # terminated by 2 tildes
)

New

~~Hi~~ Hello, world!

~~This whole sentence is wrong~~

No ~ allowed unless it is escaped

~~Not ok unless ~ is escaped~~

~~Not ok unless \~ is escaped~~

Another example: ~~ New 
line is permitted~~

Extraction

~~Hi~~ Hello, world!

~~This whole sentence is wrong~~

No ~ allowed unless it is escaped

~~Not ok unless ~ is escaped~~

~~Not ok unless \~ is escaped~~

Another example: ~~ New 
line is permitted~~