Update: As tye points out below, I was wrong.

You have to return a reference to the modifed @_ from the pre wrapper sub, if you want that to be passed to the original sub.

use strict;
use Hook::LexWrap;

sub some_sub{
    print "@_";
}

sub before{
    # inject a new arg
    unshift @_, 'new arg';
    return \@_;
}

wrap some_sub, pre =>  \&before;

some_sub(1,2,3);
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