What does "while~<>" mean?

[J Krugman]

I recently saw a Perl one-liner that ended with the construct
"while~<>". MO=Deparse was no help (it simply translated it to
"while ~<ARGV>"). I searched the Perl docs but found nothing.
What does the tilde before the <> operator mean?

Thanks!

jill

 

[Brian McCauley]

I recently saw a Perl one-liner that ended with the construct
"while~<>". MO=Deparse was no help (it simply translated it to
"while ~<ARGV>"). I searched the Perl docs but found nothing.
What does the tilde before the <> operator mean?

It is the binary not operator. It is one of the few Perl operatotions
that treats numbers differently from strings.

~1 is 4294967294 (assuming 64 bit integers)

~"\x01\x02" is "\xFE\xFD"

But this sounds like golfing to me (trying to write the smallest
possible code with no consideration given to clarity).

<> inside a while clause magically assignes $_ but ~<> supresses this.
So it simply waits for a line of input an thows it away.

foo while ~<>;

Is like

while (1) {
<>; # Pause
foo;
}

 

[Bob Walton]

J Krugman wrote: ....

~1 is 4294967294 (assuming 64 bit integers)

32---------------------------^^
....