Obtain perl expression of an entry

[banksider]

Suppose that variable x1 has value "123-". That is, x1 = "123-". If I use prxparse("/\ddd-/") and prxmatch I can return position 1 for this value. Now, if I didn't know ("/\ddd-/"), would there be a way for me to obtain ("/\ddd-/")  from  "123-"? That's, is there a way to obtain the perl regular expressions for any entry?

Thanks

[FreelanceReinh · Accepted solution]

Hello @banksider,

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@banksider wrote:

(...) x1 = "123-". If I use prxparse("/\ddd-/") and prxmatch I can return position 1 for this value.

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You mean "/\d\d\d-/", right?

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Now, if I didn't know ("/\ddd-/"), would there be a way for me to obtain ("/\ddd-/")  from  "123-"?

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The first thing I virtually always do to obtain a regular expression is to open the Tables of Perl Regular Expression (PRX) Metacharacters.

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That's, is there a way to obtain the perl regular expressions for any entry?

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I don't think there's an automated way to obtain "the" regex for any entry, simply because it is not unique: In your example there is a variety of matching regular expressions (depending on the purpose) ranging from very specific expressions such as "/123-/" to very general expressions like "/.*/". You may want to choose "/\d\d\d-/" for your purposes, but others would prefer, e.g., "/\w{3}?-/" for their purposes.