How to Fix "Single character alternation" Regular Expression Warning?

Fix for "Single character alternation" regex code inspection warning

The "Single character alternation" warning shows up in JetBrains' IDEs. The warning reports that the single character alternation (such as a|b|c) in a regular expression would be better written as a character class instead (i.e. [abc]). This might even be slightly more performant when it's matching.

For example, consider the following regular expression that allows one of the symbols from; =, :, - or _:


This could be re-written as:


Please keep in mind that in character classes, the characters ^-]\ need to be escaped.

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