This is a thing I often want to do in different situations. But I'll state the problem in the specific form in which it's just arisen.

I have an array of hashes, call it @tabs. Each hash in @tabs has several keys, including Action and Suppress. Suppress has a default value of 0. Sometimes, however, I want to turn Suppress on (i.e. set its value to 1) depending on the value of Action.

In this example I want to turn it on if Action has one of three possible values, namely GetAll Make or MakeOnly.

The obvious way to do this, and the one I usually end up with, is 
for (@tabs) {
    if (
        $_->{Action} eq 'GetAll' or
        $_->{Action} eq 'Make' or 
        $_->{Action} eq 'MakeOnly'
    ) {
        $_->{Suppress} = 1;
    }
}

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An arguably more elegant way would be 
for my $hash (@tabs) {
    if (grep {$hash->{Action} eq $_} qw/
        GetAll
        Make
        MakeOnly
    /) {
        $hash->{Suppress} = 1;
    }
}

[download]
... but, maybe it's just me, I don't like to get grep out on such a trivial pretext (pass me my twelve bore, there's a snail in the lettuce patch) - plus, it involves creating a new var. Then there's a regex 
for (@tabs) {
    if ($_->{Action} =~ /(^GetAll$)|(^Make$)|(MakeOnly$)/) {
        $_->{Suppress} = 1;
    }
}

[download]
... but that comes with an overhead. Then there's using the logical "or", 
for (@tabs) {
    if ($_->{Action} eq 'GetAll' || 'Make' || 'MakeOnly') {
        $_->{Suppress} = 1;
    }
}

[download]
... which is perfect except that, as eagle-eyed monks will have spotted it DOESN'T WORK, because 'GetAll' always returns a true value so that 'GetAll' || 'Make' || 'MakeOnly' is the same as 'GetAll' .... duh.

As you can see, I've already spent too much time thinking about this. Can some kind monk put me out of my misery, either by telling me there is no simple one line way to do this without additional overhead, or by telling me what it is?

§ George Sherston

In reply to Conditional idiom : "if X equals Y or Z" ?? by George_Sherston

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