We can also craft patterns that loop forever (not merely a long time) (well, ignoring stack overflows that is) 

#Word boundries are zero-width so the regex engine will never progress

my $inf; $inf=qr/\b(??{$inf})/;

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Did you try it? See perlre/Repeated patterns matching zero-length substring

Currently, you can mis-use \G to loop forever: 1 while "a" =~ /a|\G/g. Doesn't work in a single list-context ()="a"=~/a|\G/g though.

In reply to Re: Are Perl patterns universal? by ysth
in thread Are Perl patterns universal? by sleepingsquirrel

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