Regular Expressions 101

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"
(?<![\$])\$([^$]+)\$(?!\$)
"
g
Negative Lookbehind
(?<![\$])
Assert that the Regex below does not match
Match a single character present in the list below
[\$]
\$ matches the character $ with index 3610 (2416 or 448) literally (case sensitive)
\$ matches the character $ with index 3610 (2416 or 448) literally (case sensitive)
1st Capturing Group
([^$]+)
Match a single character not present in the list below
[^$]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
$ matches the character $ with index 3610 (2416 or 448) literally (case sensitive)
\$ matches the character $ with index 3610 (2416 or 448) literally (case sensitive)
Negative Lookahead
(?!\$)
Assert that the Regex below does not match
\$ matches the character $ with index 3610 (2416 or 448) literally (case sensitive)
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.

Regular Expression
No Match

r"
"
g

Test String