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$ perl -le'$x=+0.0; print $x; print $x<=>0' 0 ... $ perl -le'$x=-0.0; print $x; print $x<=>0' -0 0
$ perl -wle'$x=0+Infinity; print $x; print $x<=>0' inf ... $ perl -wle'$x=0+NaN; print $x; print $x<=>0' nan Use of uninitialized value in print at -e line 1.