This seems to be exposing some weird edge cases in perl. I added some extra alias/reference tests like these: 
sub by_alias { $_[0]  =~ s/\s+//; }
sub by_alias2 { for ($_[0]) { s/\s+//; } }
sub by_alias3 { ${\$_[0]} =~ s/\s+//; }
sub by_ref { ${ $_[0] } =~ s/\s+//; }
sub by_ref2 { for (${ $_[0] }) { s/\s+//; } }

[download]
I then bumped up the string size so it went in 10k increments rather than 1k, and reduced the loop count. There's a weird effect occuring when the string size switches between 130k -> 140k. 
Length of string: 130000
          Rate  alias   ref2 alias2    ref alias3
alias  17544/s     --   -67%   -67%   -68%   -68%
ref2   52632/s   200%     --    -0%    -5%    -5%
alias2 52632/s   200%     0%     --    -5%    -5%
ref    55556/s   217%     6%     6%     --     0%
alias3 55556/s   217%     6%     6%     0%     --

Length of string: 140000
          Rate alias3 alias2   ref2    ref  alias
alias3  1376/s     --    -0%    -0%    -0%   -92%
alias2  1377/s     0%     --    -0%    -0%   -92%
ref2    1379/s     0%     0%     --    -0%   -92%
ref     1381/s     0%     0%     0%     --   -92%
alias  16393/s  1092%  1090%  1089%  1087%     --

[download]
That's just bizarre. It seems for strings < 130k, something strange is occuring with @_ aliasing, and for strings > 130k, for () aliasing and references are going haywire. Very odd indeed. This is debian perl, v5.8.8 built for i486-linux-gnu-thread-multi

In reply to Re: Pass by ref vs alias : why does scalar size matter? by Anonymous Monk
in thread Pass by ref vs alias : why does scalar size matter? by clinton

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.