As others noted, this problem isn't nearly as simple as it first appears. To be safe, use Mail::Address instead of trying to create your own solution:

use Mail::Address;
my $addr = 'name@domain.com';
my $ma = Mail::Address->new('', $addr);
my $user = $ma->user;
[download]

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I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated