The following program prints "fail1, fail2": 
$T = qr//;
$U = qr//;
$_ = "12";
/(1)(2)/;
my ($t, $u) = ($1, $2);
print $t =~ /$T/ ? "pass1, " : "fail1, ";
print $u =~ /$U/ ? "pass2\n" : "fail2\n";

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Either one of these changes: 
$T = qr/./;

[download]
print $t =~ /(?:$T)/ ? "pass1, " : "fail1, ";

[download]
causes the program to print "pass1, pass2".

In reply to Empty qr// fails to match -- Is this known bug? by chibiryuu

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