or download this
sidhekin@blackbox:~$ perl -le '($c = 1) = 2; print $c'
2
sidhekin@blackbox:~$ perl -le '$c = 1 = 2; print $c'
Can't modify constant item in scalar assignment at -e line 1, near "2;
+"
Execution of -e aborted due to compilation errors.
sidhekin@blackbox:~$