What is the best way to check if a scalar variable is a file handle?

The naïve way would be to use something like ref($var) eq 'IO' but that doesn't cover things like blessed IO::File, IO::Scalar, etc objects.

Perhaps it's best to use duck typing, and check for the functionality we need, e.g. $var->can('getline') && $var->can('close')?

What do you use?

Update: is_real_fh from IO::Handle::Util and openhandle from Scalar::Util each seem close, but neither seems to identify, say IO::All objects. :-(

Another update: I've tried to consolidate some of these techniques into IO::Detect 0.001 which is now on CPAN.

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

In reply to Best way to check if something is a file handle? by tobyink

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