Re: regular expression with @@/

According to perlretut ( here ):

The escape sequence \Q ...\E quotes, or protects most non-alphabetic + characters. For instance, 1. $x = "\QThat !^*&%~& cat!"; 2. $x =~ /\Q!^*&%~&\E/; # check for rough language It does not protect $ or @ , so that variables can still be substitute +d.
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And perl.com says :

You cannot include a literal $ or @ within a \Q sequence. An unescaped $ or @ interpolates the corresponding variable, while escaping will cause the literal string \$ to be matched. You'll need to write something like m/\Quser\E\@\Qhost/.

So, escaping should work :

use warnings;
use strict;

print "Yes!\n" if ( '$@' =~ m|\$\@| ); 
# prints "Yes!"
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So maybe your regex isn't what you think - try a little debugging :

use warnings;
use strict;

my $string = '@@@';
if ( $string =~ m|\$\@| ){
    print "Yes!\n";
}
else {
    print "\'$string\' did not match...\n";
}
# prints "'@@@' did not match..."
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HTH

Update: Hmmm... damn slow typing... kennethk may have won the battle, but next time...(or not)!

Just a something something...

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Re^2: regular expression with @@/ by almut (Canon) on Dec 07, 2009 at 18:32 UTC
Actually, in this particular case, it should work with and without quoting, because `/@@/` doesn't interpolate anything (as opposed to `/@@x/` or `/\Q@@x\E/`, for example). `#!/usr/bin/perl use warnings; use strict; $_ = 'foo@@bar'; print "matched\n" if /@@/; print "matched\n" if /\Q@@\E/; print "matched\n" if /\@\@/; __END__ matched matched matched` [download] Update: maybe a better (anchored) check, avoiding the potential gotcha of matching against a single-`@` pattern: #!/usr/bin/perl use warnings; $_ = '@@'; print "1 matched\n" if /^@@\z/; print "2 matched\n" if /^\Q@@\E\z/; print "3 matched\n" if /^\@\@\z/; print "4 matched\n" if /^\Q@@x\E\z/; # doesn't match, because @x is be +ing interpolated print "5 matched\n" if /^@\@x\z/; # doesn't match, because there is + no 'x' in the string __END__ Possible unintended interpolation of @x in string at ./811585.pl line +10. Name "main::x" used only once: possible typo at ./811585.pl line 10. 1 matched 2 matched 3 matched [download]	[reply] [d/l] [select]
Re^3: regular expression with @@/ by BioLion (Curate) on Dec 08, 2009 at 11:26 UTC
Good call - as usual - I guess I more wanted to make the point that adding in some debugging is always useful, just so if things don't match, you can see exactly what they are, and tell if it is your input or your regex that isn't what you think... Just a something something...	[reply]