It looks like version tuples are not recognised when used directly as hash keys in perl5.5.650. $ perl -MO=Deparse -e '$hash{v1.2.3.4}++;' ++$hash{'v1' . 2.3 . 4}; -e syntax OK Also, with perl5.005_03 this is deparsed as: $ perl -MO=Deparse -e '$hash{v1.2.3.4}++;' -e syntax OK ++$hash{'v12.34'}; Is perl5.5.650 less clever with constant folding? And why did the "-e syntax OK" line come last with perl5.5.650? Just a buffering coincidence? Regards, GisleThread Next