What is the use of following?

i.) –w
When used gives out warnings about the possible interpretation errors in the script.

ii.) Strict
Strict is a pragma which is used to force checks on the definition and usage of variables, references and other barewords used in the script. This can be invoked using the use strict command. If there are any unsafe or ambiguous commands in the script, this pragma stops the execution of the script instead of just giving warnings.

iii.) -T.
When used, switches on taint checking which forces Perl to check the origin of variables where outside variables cannot be used in system calls and subshell executions.