APM: Regular expression with double variable substitution

[Evan Harris]

Is there any way to make perl re-interpret the contents of a variable that
is used as a substitution part of a regex?  I thought that the /e modifier
would do this, but it doesn't seem to work.

For example:

$s = '$1 - $2';
$t = '34:56';
$t =~ s/(\d+):(\d+)/$s/e;

After this, $t is equal to '$1 - $2', rather than the desired '34 - 56'.

I think it may be possible by using an eval, but I don't want the power (and
the danger) of allowing any perl code, I just want to fill in nested
variables.

Evan