Let's say the character NO-BREAK SPACE (U+00A0) appears in a UTF8-encoded text
file (so it appears there as C2A0), and I want to match strings that contain
this character.
I write a script (itself encoded with UTF8) in Perl 5.10.0 (on OS X 10.6.5)
with:
use encoding 'utf8';
use charnames ':full:';
The script opens the file with:
open FH, '<:utf8', filename.txt;
It reads lines in with:
while <FH> {}
Then, in a regular expression in the script, I can match the NO-BREAK SPACE
with any of these patterns:
1. /\N{NO-BREAK SPACE}/
2. / / (where the character between slashes looks like a space but is a
no-break space)
3. /[\x7f-\x80]/
Patterns 1 and 2 make sense, but pattern 3 is mysterious to me, because the
range specified in pattern 3 includes DELETE and an unnamed character but does
not include NO-BREAK SPACE.
Moreover, I expect to be able to match the NO-BREAK SPACE with these patterns,
but I cannot:
4. /[\xa0]/
5. /\xa0/
In the related documentation, I have not found anything explaining why pattern
3 works, or anything explaining why patterns 4 and 5 do not work.
I have replicated these anomalies in Perl 5.8.8. under Red Hat Enterprise Linux
5.
I would be delighted to receive explanations or references to documentation
that I have overlooked or misunderstood.
ˉ
