#! perl -w
use strict;


# 1: no problem (even on Win32)
#
my $root = 'C:/perl';
my $podfile = 'C:/Perl/lib/Config.pm';
print "$podfile   $root   $1   $2\n" if $podfile =~ m!$root/(.*)/(\w+)\.p.+$!i;


# 2: causes error
#
my $rootb = 'C:\perl';
my $podfileb = 'C:\Perl\lib\Config.pm';
print "$podfileb   $rootb   $1   $2\n" if $podfileb =~ m!$rootb/(.*)/(\w+)\.p.+$!i;


# 3: simplified, causes error
#
print "yo\n" if 'perl' =~ m|\perl|;


__END__

##</code><code>##

In addition, Perl defines the following:

...

    \pP Match P, named property.  Use \p{Prop} for longer names.

    \PP Match non-P

##</code><code>##

print "==$Config{installprefix}==\n";	# prints ==C:\Perl==

##</code><code>##

$podfileb =~ s!\\!/!g;
$rootb =~ s!\\!/!g;