\s is suppose to match U+00A0 and sometimes does. It's a bug in Perl that cannot be fixed for backwards compatibility reasons. You can indicate you want the fix using feature unicode_strings. In earlier versions of Perl, you can also work around the bug by upgrading the string's internal format. 

use strict;
use warnings;
use feature qw( say );

my $string = chr(160);

no feature qw( unicode_strings );
say $string =~ /^\s*$/ ? 1 : 0 ;     # 0

use feature qw( unicode_strings );
say $string =~ /^\s*$/ ? 1 : 0;      # 1

no feature qw( unicode_strings );
utf8::upgrade($string);
say $string =~ /^\s*$/ ? 1 : 0;      # 1

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In reply to Re: Can I change \s? by ikegami
in thread Can I change \s? by pileofrogs

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