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'

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In reply to Re: I've never seen this before - $#a = 4 - ?? by mfriedman
in thread I've never seen this before - $#a = 4 - ?? by emilford

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