Laurent is right, have a look at these two posts/subthreads to get a good idea of how fast Perl's hashes are:

Re: Determining uniqueness in a string. (giant hash lookup...)
Re^2: Determining uniqueness in a string. (...versus a tiny Inline::C function)

In reply to Re^3: Appending values to existing hash key by hazylife
in thread Appending values to existing hash key by jaypal

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