I start all of my scripts with the following shebang. [...]

#!/usr/bin/env perl
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Digging into the details, this starts the env program, which then searches for the first perl executable in $ENV{PATH}. So this increases the startup time slightly. Also, env is not always in /usr/bin. Some Linux distributions put it into /bin and add a symlink in /usr/bin. Some other Unixes have env only in /bin, with no symlink in /usr/bin. In that case, all of your scripts will simply fail. See also far more you ever wanted to know about #!.

Alexander