The match operator will happily interpolate a pattern stored as a string. Compiled patterns have only existed since 5.6. qr// is not necessary.

In fact, using qr// makes no sense here.

If there's no reason for the pattern to be a string, you might as well just do

$string = 'My Test Data';
print $string =~ m/\btest\b/i ? "Match\n" : "No match\n";
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But I bet there's a reason it's a string here. If so, you'd do

$string = 'My Test Data';
$regex = '(?i)\btest\b';
print $string =~ $regex ? "Match\n" : "No match\n";
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If you were planning on using $regex repeatedly, then qr// could become useful.