(bug) search error: tagged expr. and '\n' in search text

[sosimple]

If I compose a multi-line search with a "tagged expression", and a reference to the "tagged expression" within the search text (on a different line), the search fails with an error: "Invalid regular expression"

A simple example...
Document text:

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..Some text here...
abc
abcdef
ghighi
jkl
more text here...

Search text:

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Find what: ^(.+)\n\1(.+)
[x] Regular expression

And:

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[x] POSIX regular expression syntax

This should find:

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"abc
abcdef"

But, when I click "Find Next", I get an error alert:
"Invalid regular expression"

If the reference to the "tagged expression" is on the same line as the "tagged expression", then it works fine ...

Search text:

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Find what: ^(.+)\1\n(.+)
[x] Regular expression

Successfully finds:

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ghighi
jkl

I have not found this issue in the general forum, or in the "Known Problems" section.

Kevin

[ben_josephs]

The search phrase back-reference matches several postings. For example:

The way TextPad's regex recogniser handles newlines is very weak. It doesn't allow a \n to be quantified with * or + or {m,n}, or to be contained in a parenthesised expression. And (the one relevant to your example) it doesn't allow a back-reference to refer back over a newline.