The regex that originally triggered the segfault was an attempt at a joke that used a modified version of the regex I wrote in this node.

The joke was that someone in an irc channel at work said "<3", and someone else asked what the opposite of "<3" was. My response was qr[(??{/^<3/?qr/\A\z/:qr//;})]

Which is this when written in a legible manner:

my $negative = qr[ 
  (??{
    /^<3/ 
      ? qr/\A\z/ 
      : qr//;
  })
]x;
[download]

Which segfaulted, but only when the text being searched started with '<3'. After a little exploration I found the minimal regex that still segfaulted, and posted about it.