escaped \n in regex

powerman has asked for the wisdom of the Perl Monks concerning the following question:

Is any know why '\' at end of line in regex is ignored (perl 5.8.0)? Is this a bug or feature? ;-) It's unusual for perl to have no special meaning for cool thing like this... ;-)

# 2 lines regex, \n not escaped
$re1 = qr/as
sd/;
# 2 lines regex, \n escaped
$re2 = qr/as\
sd/;
for ($re1, $re2) {
        print "$_\n";
        print "ok1\n" if "as\nsd" =~ /$_/;
        print "ok2\n" if "as\\\nsd" =~ /$_/;
        print "ok3\n" if "assd" =~ /$_/;
        print "ok4\n" if "as\\sd" =~ /$_/;
}
__END__
(?-xism:as
sd)
ok1
(?-xism:as\
sd)
ok1
[download]

Comment on escaped \n in regex Download Code

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Re: escaped \n in regex by pfaut (Priest) on Feb 20, 2003 at 00:31 UTC
Perl doesn't do things to be 'cool'. It does things to be useful. Besides, what 'cool' thing did you expect perl to do with that, anyway? You embedded a literal newline in your regular expression. That matches newlines in the string you match against as you can see by your test code. Putting a backslash in front of it does nothing since it's not a special character. `--- print map { my ($m)=1<<hex($_)&11?' ':''; $m.=substr('AHJPacehklnorstu',hex($_),1) } split //,'2fde0abe76c36c914586c';` [download]	[reply] [d/l]
Re: escaped \n in regex by steves (Curate) on Feb 20, 2003 at 00:34 UTC
I think this is consistent. Perl lets you embed hard newlines in string literals, which are taken for what they are -- newlines. Double quoted interpolation rules also say that \ followed by anything that's not a recognized metacharacter sequence interpolates to the character following the backslash. This is why the two above are equivalent ... which is what I think the question is.	[reply]
Re: escaped \n in regex by Pardus (Pilgrim) on Feb 20, 2003 at 13:28 UTC
Its a feature, since the line break is just an other non-special ascii char it's escaped version behaves exactly the same as any other non-special escaped char, i.e. it is just the same as the ascii char itself. -- Jaap Karssenberg \|\| Pardus (Larus)? <pardus@cpan.org> >>>> Zoidberg: So many memories, so many strange fluids gushing out of patients' bodies.... <<<<	[reply]