http://www.perlmonks.org?node_id=177463


in reply to I've never seen this before - $#a = 4 - ??

That can be used to allocate memory for an array before filling it up. It created five elements in @a and sets them all to undef.

Here's an example:

perl -MData::Dumper -e '$#foo = 4; print Dumper \@foo'