Hi Yang,
> sub ok ($;$) { } and sub is ($$;$) { }
Those are subroutines with prototypes. `sub NAME(PROTO)`
`sub ok ($;$)`
Requires one mandatory argument and an optional one. They are
separated by a semi-colon in the prototype definition. The arguments
will be considered in scalar context (due to the `$`).
`sub is ($$;$)`
Requires two mandatory arguments and an optional one. All of them will
be considered in scalar context.
See `perldoc perlsub` for more information.
Regards,
Alan Haggai Alavi.
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