This is coming up quite frequently lately... as a side note, it's not a real answer to your question, but are you sure you're using the correct data structures for your problem?

What about a hash?

my @months=qw/JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC/;
my %whatever;
$whatever{$_}=0 for @months;
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or

@whatever{@months}=(0) x @months;
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If you really need to create all those vars then I may suggest to use a "special hash", i.e. to mangle the symbol table. But this is seldom the case and I strongly doubt it is for you, so I'm not proceeding in this sense...