I was revisiting Negating Regexes: Tips, Tools, And Tricks Of The Trade and caused perl to segfault with one of the patterns I tried. I reduced the pattern to he simplest form that still causes a problem. Tested with: 
This is perl, v5.8.7 built for i486-linux-gnu-thread-multi
Characteristics of this binary (from libperl):
  Compile-time options: MULTIPLICITY USE_ITHREADS USE_LARGE_FILES
                        PERL_IMPLICIT_CONTEXT

[download]

This works: 

  "1" =~ qr[(??{/^1/})]

[download]
This segfaults 
  "<" =~ qr[(??{/^</})]

[download]
Segfault re=debug output: 
Freeing REx: `","'
Compiling REx `(??{/^</})'
size 4 Got 36 bytes for offset annotations.
Compiling REx `^<'

size 4 Got 36 bytes for offset annotations.
first at 2
   1: BOL(2)
   2: EXACT <<>(4)
   4: END(0)
anchored `<' at 0 (checking anchored) anchored(BOL) minlen 1
Offsets: [4]
        1[1] 2[1] 0[0] 3[0]
first at 1
   1: LOGICAL[2](2)
   2: EVAL(4)
   4: END(0)
minlen 0 with eval
Offsets: [4]
        10[0] 10[0] 0[0] 11[0]
Matching REx `(??{/^</})' against `<'
  Setting an EVAL scope, savestack=15
   0 <> <<>               |  1:  LOGICAL[2]
   0 <> <<>               |  2:  EVAL
  re_eval 0x8153fe8
Guessing start of match, REx `^<' against `<'...
Guessed: match at offset 0
Matching REx `^<' against `<'
  Setting an EVAL scope, savestack=15
   0 <> <<>               |  1:  BOL
   0 <> <<>               |  2:  EXACT <<>
   1 <<> <>               |  4:  END
Match successful!
Compiling REx `1'
size 3 Got 28 bytes for offset annotations.
first at 1
   1: EXACT <1>(3)
   3: END(0)
anchored `1' at 0 (checking anchored isall) minlen 1
Offsets: [3]
        1[1] 0[0] 2[0]
Entering embedded `1'
  Setting an EVAL scope, savestack=21
   0 <> <<>               |  1:  EXACT <1>
                            failed...
Freeing REx: `"1"'
                          failed...
  Setting an EVAL scope, savestack=24
   1 <<> <>               |50339:  LOGICAL[2]
   1 <<> <>               |50340:  EVAL

[download]
Is this fixed in later perls?

In reply to regex bug in perl 5.8.7 by imp

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.