Nice. It's fundimentally the same, but you get a lot of collapse of excess code by folding up the if/else decision when computing $value.

I would normally, in any language, spot that construct: 

if (something)
   value = xxxxx
else
   value = yyyy

[download]
as something to be folded up into one expression. Perhaps a terinary operator: value = (something) ? xxxxx : yyyy. But the "defined or" really shines here, reeling in the rest. That is precisely the idiom that the OP needs in the problem: grab the value at the source coordinates, but make it '' instead of undef.

I see that the computation of max_col was made into one line by using the suffix form of 'for'. That shrunk the vertical expanse of code down quite a bit.

In reply to Re^2: Pivoting 2 dimensional array refs by John M. Dlugosz
in thread Transposing 2 dimensional arrays by Voronich

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