"#!/Users/user/perl5/perlbrew/perls/perl-5.14.1/bin/perl5.14.1"

That shebang line locks the script into using a single version of Perl. While that might be what you want in some circumstances, I don't think that would be the norm.

This shebang line (which I indicated in "Re^3: Can't locate Email/MIME.pm in @INC" below) allows you to upgrade Perl and use it with all your scripts without having to edit every one of those scripts.

#!/usr/bin/env perl
[download]

It also makes it easy to test your current codebase with new versions of Perl: a single "perlbrew switch new-perl-version" to check for backward-compatibility and a single "perlbrew switch old-perl-version" to rollback (if that's required).