To be honest, interpolating strings is best done in a format slightly unlike perl. For example, using Text::Template or something. However, if you can completely trust your input to not do something silly (for example, it's written by you or a teammate, and not coming in from a web user or marketing), your method is fine.

  my $interpolated = eval(qq("$need_to_interpolate"));
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Slightly simpler, slightly easier to read, IMO.