>perl -wle"no warnings 'uninitialized'; print '' + 4"
Argument "" isn't numeric in addition (+) at -e line 1.
4

>perl -wle"no warnings 'numeric'; print '' + 4"
4

##</code><code>##

>perl -Mdiagnostics -wle"print '' + 4"
Argument "" isn't numeric in addition (+) at -e line 1 (#1)
    (W numeric) The indicated string was fed as an argument to an operator
    that expected a numeric value instead.  If you're fortunate the message
    will identify which operator was so unfortunate.

4