perl -wle 'print ("foo")' # Warning perl -wle 'print ("foo");' # No warning perl -wle 'print (")");' # Warning perl -wle 'print ("\x29");' # No warning #### $ perl -wle 'print ("foo") . "bar"' print (...) interpreted as function at -e line 1. Useless use of concatenation (.) or string in void context at -e line 1. foo $ perl -wle 'my $s = length ("foo") . "bar"'