Question

So I am a beginning Perl programmer. I have been using it for about a month, however only in the last week or so have I been using it for anything other than sysadmin type tasks. In doing so I ran into the following question,

Perl subprocesses are really flexible, and they don’t impose many/any constraints on arguments you pass in. How is it possible to either enforce the number of arguments and/or check whether they’re references, scalars etc etc?

To clarify, here’s what I currently do for Perl subprocesses:

sub mySub{
    ($a, $b) = @_;
    continue and use these methods
 }

But this provides no guarantees about what $a and $b hold. Is there anyway to make sure they contain values, say a reference for $a and a scalar for $b?

Thanks in Advance.

EDIT: When I said scalar for $b I mean containing an integer, and not being a reference to some other datastructure.

Answer 1

You can use the Params::Validate module, it provides wide possibilities of checking the argument list.

In your case, something like

validate_pos(@_, { type => HASHREF | ARRAYREF }, { type => SCALAR })

would do it (note that it doesn’t have a single type for “ref”). It dies when the parameters don’t match.