Regular Expressions 101

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"
->\s(\w+:\s\w+(?:==)?)\s<-
"
gm
->
matches the characters -> literally (case sensitive)
\s matches any whitespace character (equivalent to [\r\n\t\f\v  ])
1st Capturing Group
(\w+:\s\w+(?:==)?)
\w
matches any word character (equivalent to [a-zA-Z0-9_])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\s matches any whitespace character (equivalent to [\r\n\t\f\v  ])
\w
matches any word character (equivalent to [a-zA-Z0-9_])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?:==)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
==
matches the characters == literally (case sensitive)
\s matches any whitespace character (equivalent to [\r\n\t\f\v  ])
<-
matches the characters <- literally (case sensitive)
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.

Regular Expression
No Match

r"
"
gm

Test String