There is no magic here and map() has no special knowledge of $1 or any other number variable. Regular expression matches in list context return the contents of any matched grouping. In your case you have exactly one capture group so m// returns $1 which becomes the return value of the map() block and viola!, map() uses $1. But only indirectly.

In reply to Re: maps implicit "$1-handling" by diotalevi
in thread maps implicit "$1-handling" by tos

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