> When does the structure get built? That's why eg. tr[a-z][A-Z]
> brooks no variables, for it is solely at compile time that these
> things occur, and why you must resort to delayed compilation via
> eval qq/.../ to prod the compiler into building you a new one.
Certainly. But if there were no variable interpolation for regexes,
you could make the same argument about regexes. I don't see any
reason why the regex solution couldn't or shouldn't be extended to
tr/// also. If the pattern and replacement sets contain variables,
then table construction can be deferred until run time; if there are
no variables, the table is computed at compile time.
Building a tr/// table is much much simpler and much less work than
compiling a regex, but we don't make people write
eval " \$s =~ m/$pat/ "
when they want to interpolate a string into a regex at run time.
Instead, we take care of it transparently. tr/// could easily be made
to work the exact same way.
> Maybe you want qt/.../.../ or something.
I don't think a new notation is necessary in this case. All that's
needed is a small extension to the existing semantics, in a direction
that has already been thoroughly investigated.
