Sorry for nitpicking, but in praxis this only works with a string where all groups match, "" isn't enough.

use 5.010;
"" =~ /(?<mon>\w+)\s(?<mon>\w+)/;
print scalar keys %-;                  # 0

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Now constructing such a string is in general even more difficult than just parsing for named captures labels.

Good idea anyway! :)

Cheers Rolf

In reply to Re^2: How do I extract named variable names from regex string by LanX
in thread How do I extract named variable names from regex string by maspsr

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