like chihuahuas to a pork chop, we're drawn to this question...
here's a novel way of doing it :

@numbers = (6,210, 3);   # not necessarly consecutive
$templ="test X number ";
print join "\n", map{($str = $templ)=~s/X/$_/?$str:undef}(@numbers);
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just remember that map is chief among the ob-fu master's tools. Use it wisely, and only after considering a for loop or foreach loop, or you may be writing some code that'll come back to haunt you.