/^([\d.-]*\d[\d.-]*)$/ looks so innocent.
It is however a very inefficient regex. Because you give
Perl lots of ways of matching the lone
\d,
it can take a relatively long time for Perl to determine
there is a failure. Dropping the
\d from the
first character class make a huge difference:
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw /cmpthese/;
our $re1 = qr /^[\d.-]*\d[\d.-]*$/;
our $re2 = qr /^[.-]*\d[\d.-]*$/;
our @strs = <DATA>;
our (@d, @a);
foreach (@strs) {
die if /$re1/ xor /$re2/
}
cmpthese -1 => {
davido => 'my @a = map {/$re1/} @strs',
abigail => 'my @a = map {/$re2/} @strs',
}
__DATA__
--1--2--3--4--5--6--7--8--9--0--1--2--3--4--5--6--7--8--9--0--a--2--3-
+-4--5--
Rate davido abigail
davido 23578/s -- -88%
abigail 196495/s 733% --
Abigail
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