Bitten by over thinking the plumbing. Change the colsMap line to:

$table->colsMap( sub {$_->[0] =~ s/,/\./g; $_->[2] = $_->[0] * $_->[1]
+ } );
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and the code prints:

Numbers,Values,Result
100.20,2,200.4
18.20,3,54.6
19.45,2,38.9
7.25,2,14.5
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which I suspect is what you were after.

The result of $_->[0] =~ s/,/\./g is true (1) if there was a match. You were expecting the resulting value of $_->[0] perhaps?