No, I'm running 5.20.1, at least on my pc. I took out the use 5.010 and the results are pretty much the same -- something is happening, but nothing good. Yes, study takes the time to build a table to make searching more efficient, something akin to a database index. If the strings are short, or there are only a very few searches to perform, study isn't worth the effort. I should really try it on a sample problem like the one suggested in the docs.

No, the study keyword does absolutely nothing except return an appropriate boolean for backwards compatibilty. In particular, it is not building up any tables. Here is the C source code for pp_study() in 5.18.0:

PP(pp_study)
{
    dVAR; dSP; dPOPss;
    STRLEN len;

    (void)SvPV(sv, len);
    if (len == 0 || len > I32_MAX || !SvPOK(sv) || SvUTF8(sv) || SvVAL
+ID(sv)) {
    /* Historically, study was skipped in these cases. */
    RETPUSHNO;
    }

    /* Make study a no-op. It's no longer useful and its existence
       complicates matters elsewhere. */
    RETPUSHYES;
}
[download]

Dave.

something is happening,

I'm guessing the differences you are seeing is just down to the overhead of calling into C, doing (almost) nothing, and returning again.

From pp.c/5.18

/* Pattern matching */

PP(pp_study)
{
    dVAR; dSP; dPOPss;
    STRLEN len;

    (void)SvPV(sv, len);
    if (len == 0 || len > I32_MAX || !SvPOK(sv) || SvUTF8(sv) || SvVAL
+ID(sv)) {
    /* Historically, study was skipped in these cases. */
    RETPUSHNO;
    }

    /* Make study a no-op. It's no longer useful and its existence
       complicates matters elsewhere. */
    RETPUSHYES;
}
[download]

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