sub func { return (0, 1, 2) }

if (1 and do { ($result) = func($param); $result }) {
   print "1\n";
} else {
   print "0\n";
}

if (1 and ($result) = func($param)) {
   print "1\n";
} else {
   print "0\n";
}

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outputs 
0
1

[download]
($result) = func($param)

[download]

is a list assignment, and it happens to be in scalar context. List assignment in scalar context returns the number of elements returned by its RHS. (See Mini-Tutorial: Scalar vs List Assignment Operator.)

If func returns three values, the second snippet is equivalent to 

if (... and do { ($result) = func($param); 3 })

[download]

which is different than 

if (... and do { ($result) = func($param); $result })

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As shown above, the difference will matter when func returns more than one value and the first is false.

You can avoid the do using a list slice. 

if (... and $result = (func($param))[0])

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Scalar assignment returns its LHS.

In reply to Re: Is there any difference between these two statement? by ikegami
in thread Is there any difference between these two statement? by PerlOnTheWay

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