I'm in the process of writing a couple of "shortcut" functions, but I'm unsure about implementing the best semantics for the functions. I'm not sure whether the functions should silently take '$_' as an argument when the function is called with zero arguments as seems to be the case with the standard "shortcut" idiom. Using trim from Trim::Text as an example: 
sub trim {
    @_ = @_ ? @_ : $_ if defined wantarray; # disconnect aliases in no
+n-void context

    for (@_ ? @_ : $_) { s/\A\s+//; s/\s+\z// }

    return wantarray ? @_ : "@_";
}

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On the one hand, it allows perlish natural use of the function, such as: 
foreach (@args) { 
    <...>; 
    trim; 
    <...>;
}

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But, on the other hand, empty argument lists may bite you by operating unexpectedly on '$_': 
foreach (@args) {
    my @b;
    <...>
    @b = ();
    trim(@b); # silently the same as trim($_) since @b has no elements
    <...>;
}

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I'm honestly tempted to rewrite the "shortcut" function as: 
sub trim {
    if ( !@_ && !defined(wantarray) ) { carp 'Useless use of trim with
+ no arguments in void return context (did you mean "trim($_)"?)'; ret
+urn; }
    if ( !@_ ) { carp "Useless use of trim with no arguments"; return;
+ }
    @_ = @_ if defined wantarray;

    for (@_) { s/\A\s+//; s/\s+\z// }

    return wantarray ? @_ : "@_";
}

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In the best of all worlds, I'd rewrite the function to differentiate between "trim()" and "trim( () )". But, given the implementation of subroutine argument passing, I haven't come across or originated any way of doing that. (Let me know if you have...)

So, what's the prevailing wisdom on this?

Thanks.

- Wyrd

In reply to Is silent use of $_ for empty argument lists reasonable for "shortcut" functions? by Wyrdweaver

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