Little-used features of Perl

Little-used features list:

	-P option
	-u option
	dump
	...
	.. in scalar context
	formats:
	    in general
	    $: to control line breaking in a ^.... field
	    $% current format output page number
	    $= format number of lines per page
	    $^L format form feed character
	    $- format number of lines left on current page
            formline

	s'''
	?...?
	reset to reset ?...? matches
	reset to undef variables
	$x{$k1,$k2} and $;
	Symbol table hash %P::
	Function exporting with *foo = *bar
	$^P debugger mode variable
	study	
	$+
        sin, cos, atan2
        log, exp
        rewinddir
        getprotoent, getprotobyname, endprotoent, etc.
        msg*
        sem*
        shm*
        fileno
        ioctl
        fcntl
        $#
        syscall
        package;

Responses:

	I personally have used that feature more than once.
	I used that feature once.
	I have never used that feature, but I am familiar with it
	   and I have seen other people use it.
	I have never seen anyone use that feature, but I am familiar with it.
	I was aware of that feature, but was not familiar with the details.
	I had no idea there was such a feature.

I've used a surprising number of these; not always for good reasons. package; I've used in the past, but now gives a syntax error, at least as of 5.10.0. -- PJF