Bug #132726 for Regexp-Common: /^$RE{URI}$/ takes exponential time depending on the position of an invalid percent-encoding

Hello, Matching /^$RE{URI}$/ against a URL with an invalid percent-encoding takes exponential time. The further down the string the incriminating percent characters is, the longer it takes. See the demo program below. Anchoring at the beginning and the end of the string is important. Using /^$RE{URI}{HTTP}$/ works fine, though. This is on perl 5.28, Regexp::Common 2017060201, macOS 10.15.4. But the same behaviour occurred on Linux with a different perl version. Thank you, Marcel Demo: #!/usr/bin/env perl use strict; use warnings; use v5.10; use Regexp::Common qw(URI); use Time::HiRes qw(gettimeofday tv_interval); # constant time say "RE{URI}{HTTP}\n"; run(qr/$RE{URI}{HTTP}/); # exponential time (sometimes) say "\nRE{URI}\n"; run(qr/$RE{URI}/); sub run { my $re = shift; for my $pos (24 .. 49) { my $uri = 'http://www.example.com/zzzzzzzzzzzzzzzzzzzzzzzzzz'; substr($uri, $pos, 0) = '%'; my $t0 = [gettimeofday]; $uri =~ /^$re$/; my $elapsed = tv_interval($t0); say "$uri $elapsed"; } }