That's because it isn't available in the default perl 5.8.8: 
> perl -Mstrict -w -e'my $f;  print ($f // "something\n")'
print (...) interpreted as function at -e line 1.
Search pattern not terminated at -e line 1.

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"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re^4: complaint: always testing defined() by Joost
in thread complaint: always testing defined() by RaptorRex

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