Useless use of a variable in void context

##</code><code>##

lorien:~$ perl -wle '$SIG{__WARN__}=sub{print"TRAPED"};s///'
TRAPED
TRAPED
lorien:~$  perl -wle '$SIG{__WARN__}=sub{print"TRAPED"};$.,$.=0'
Useless use of a variable in void context at -e line 1.
lorien:~$  perl -wle 'BEGIN{$SIG{__WARN__}=sub{print"TRAPED"};}$.,$.=0'
TRAPED

##</code><code>##

lorien:~$  perl -wle '$SIG{__WARN__}=sub{print"TRAPED"};eval q{$.,$.=0;}'
lorien:~$
lorien:~$  perl -wle '$SIG{__WARN__}=sub{print"TRAPED"};eval {$.,$.=0;}'
Useless use of a variable in void context at -e line 1.
lorien:~$