If you really want to do that, and I strongly recommend that you don't, then add the following to your .emacs
in reply to Specific Indentation request for perl in Emacs
You can also customize the cperl-indent-parens-as-block variable so as not to confuse customize later.
Why do I recommend you don't do that? Because indenting parenthesized expressions the same way as a block can create confusion in the reader. If you've got a problem with the right margin encroaching, you can always reindent as follows:
(setq cperl-indent-parens-as-block t)
And what do you know? You claw back some vertical space, which is never a bad thing.
my $var =
$new->function( arg1 => 1, );