I’ve never used Perl but I periodically mistake eq and = in bash scripts. It’s quite annoying since there’s no obvious indication that one is for numbers and one is for strings.
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Everything in computers (and I may say, more in general in life) is based on assumptions made on knowledge we implicitly have. After a while, writing eq or == becomes natural and you stop mixing them up. These kinds of errors are frequent when you don't use something daily; for instance, after more than a decade I still keep forgetting Powershell's syntax because I don't use it often and when I do, I tend to do basic things.