Still occurs with Strawberry Perl 5.36.1 and 5.38.0 (see below) although I suspect it is more generic than Strawberry Perl.

Running the code through nytprof shows 1000001 calls to main::CORE:substcont at line 10 take most of the time.

It does not happen when the $x repetition is set to 1e5. There was a possibly related thread here a few months ago about character repetitions and COW but I can't locate it right now.

0.224835157394409
0.228233814239502
v5.22.3

9.92650699615479
0.662662982940674
v5.28.0

8.49285101890564
0.744230985641479
v5.36.1

8.02936911582947
0.788676977157593
v5.38.0

[download]

In reply to Re: Substitution unexpectedly very slow, in Strawberry by swl
in thread Substitution unexpectedly very slow, in Strawberry by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.