By labelling it, you're giving a reason for a bare-block.

In this specific case, it can be done without a bare block:

my $age;
do {
    print "Please enter your age: ";
    chomp ($age = <STDIN>);
} while $age =~ /\D/;
print "Got it: $age\n";
__END__  
Please enter your age: hi there
Please enter your age: 123abc
Please enter your age: 99
Got it: 99
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