> I couldn't figure out the "substr" part in the online examples

please note that you can alternatively use the substr function as an lvalue

substr EXPR,OFFSET,LENGTH = REPLACEMENT

which should be easier to figure out.

Cheers Rolf
(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :)
Wikisyntax for the Monastery

In reply to Re^3: Highlighting only captured groups from larger regex by LanX
in thread Highlighting only captured groups from larger regex by Polyglot

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