Add tests for RT #84294 /((\w+)(?{print $2})){2,2}/ problem

Add tests for RT #84294 /((\w+)(?{print $2})){2,2}/ problem

Original ticket reports:

    print "Match: \$1=$1 \$2=$2" if 'ab' =~/^((\w+)(?{print defined $2 ? "\$2=$2\n" : "\$2 not defined\n"})){2}$/;

Produces the following incorrect output:

    $2=ab
    $2 not defined
    $2=b
    Match: $1=b $2=b

It should produce:

    $2=ab
    $2=a
    $2=b
    Match: $1=b $2=b

This adds a TODO test to verify this behavior.