2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
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Fortunately this behaviour has been fixed in perl 5.7.2 :)

[gellyfish@orpheus gellyfish]$ perl5.7.2 -e'undef christmas'
Can't modify constant item in undef operator at -e line 1, at EOF
Execution of -e aborted due to compilation errors.
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/j\