Unfortunately, unlike C, Perl has to contend with something a little crazier: Tied hashes and arrays.

And function calls. In 

  t = x->y->z->a->b[5];

[download]
any of y, z, or a can be methods, with or without side-effects, and with no guarantee that they'll return the same thing on subsequent calls. In the face of such flexibility, static analysis optimizations are non-starters.

In reply to Re: Perl and common subexpressions by dws
in thread Perl and common subexpressions by Stevie-O

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