% perl -v
This is perl, v5.6.0 built for i386-openbsd 
[...]
% perl -lwe 'print q{foo@bar.com}'
foo@bar.com
% perl -lwe 'print qq{foo@bar.com}'
In string, @bar now must be written as \@bar at -e line 1, near "foo@bar"
Execution of -e aborted due to compilation errors. 

  --versus--

% perl -v
This is perl, v5.6.1 built for i686-linux  
% perl -lwe 'print q{foo@bar.com}'
foo@bar.com
% perl -lwe 'print qq{foo@bar.com}'
Possible unintended interpolation of @bar in string at -e line 1.
Name "main::bar" used only once: possible typo at -e line 1.
foo.com