The math means that it constructs the hash from:

:

print "$_ :", $_ + $_ % 2 -1 for 0 .. 11;;
0 : -1
1 : 1
2 : 1
3 : 3
4 : 3
5 : 5
6 : 5
7 : 7
8 : 7
9 : 9
10 : 9
11 : 11

[download]

(Remember the zeroth element!).

The purpose (I guess) is to avoid the "Odd number of elements in hash assignment" warning,

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re: What's the construction? by BrowserUk
in thread What's the construction? by minaevd

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