my $stringnum = "\$string" . $num;

  my $result = eval $stringnum;
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(Note: I gave monarch a chance to fix his own article in /msg, but he blew me off in /msg and is now ignoring me, so I have to make this a public comment instead. I think that qualifies as "trying to do the right thing first".)

Please don't use eval for this without adding a big "don't do this, though". It invokes the compiler needlessly, and it also encourages variable variables, which is a broken form of programming.

I'd elaborate, but other answers in this thread already have better solutions. I just needed to flag monarch's solution as bad since he was unwilling to do that himself.