Making 5.1.1 not match 58180

[inspleak]

Hey guys.. one more quick question and I promise I will leave you alone for a bit

Essentially all I want to do is match the string "5.1.1".
However I have noticed that PERL treats the '.' as a special character and '\.' doesn't seem to change it. The following code gets a match for "5.1.1" and "58131". So, how do I get 5.1.1 to only match 5.1.1 and not 58131?

Code:
@testArray = ("5\.1\.1",);

$testme = "58131";

$currentThing = $testArray[0];

if($testme =~ /$currentThing/i)
{
print "It Matches!\n";
}
else
{
print "No Match!\n";
}

Thank you so much for your help, again.

 

[mikevh]

1. Enclose it in single quotes instead of double: '5\.1\.1'
or
2. Double the backslashes: "5\\.1\\.1"
or
3. Do a simple string comparison instead of an re match and
forget about backslashes, e.g.

@testArray = ("5.1.1",);
$testme = "58131";
$currentThing = $testArray[0];

if($testme [b]eq[/b] $currentThing) {
    print "equal!\n";
} else {
    print "not equal!\n";
}

 

[inspleak]

That worked great! Thanks so much!
This leads me to one more question then... why two '\' characters? Why doesn't one work by it self?

Thanks again!

 

[mikevh]

I don't know why. This is just something I discovered by trial and error myself. To get a single backslash into a double-quoted string, you need 2 backslashes. In a single-quoted string, you only need one.

 

[ishnid]

The correct way to quote a regular expression for use later is to use qr//:

@testArray = (qr/5\.1\.1/);

As for the double backslash, the easiest way to see this in action is just to print a double-quoted string containing backslashes:

print "5\.1\.1\n";

That will print 5.1.1, which is what will get passed to the regexp engine in your example. To get the desired effect (i.e. a literal backslash character), you'd have to escape the backslashes. Now you can see why it'd match 58131. (Incidentally, it is this behaviour that makes regular expressions in Java a severe pain in the behind).

 

[mikevh]

Thanks, ishnid. I don't think qr// was available when I started using Perl (or perhaps I just didn't know about it), so I got in the habit of using single quotes. I'll have to make myself start using qr//.

 

[inspleak]

ahh.. I see.. thanks for the explanation! It really does make sense..

 

[duncdude]

might be a silly question but are you trying to analyse the version of Perl?

if ($^V eq v5.6.1) {
print "accept\n";
} else {
print "reject...\n";
}


Kind Regards
Duncan

 

[inspleak]

Nope... but thanks for the info... Didn't know you could get the version that way.. pretty cool.

Thanks!