perl script/regex to avoid a particular pattern

Question

I am trying to look for a pattern in files and perform an operation if the pattern is found. The pattern is class <class_name> extends . But I want to exclude the case in which I encounter the pattern //class <class_name> extends ie I want to skip the operation when I get commented lines.

open my $fh, "<", $file_t or die "can't read open '$file_t': $OS_ERROR";        # Opening the file
while (<$fh>) {

    if(/class\s{1,10}<class_name>\s{1,10}extends/){
        #Perform the operation if we find above pattern
    }
 close $fh or die "can't read close '$file_t': $OS_ERROR";                      #Closing the file
}

How do I include the piece of code to exclude the pattern I mentioned. Thanks for the help.

***********Edits************

I think I have to re-frame my question. I also want to ensure that when I look for class <class_name> extends I should look for that pattern only and not if that pattern exists along with a // before it. Something like, doing a "if and only if" that particular pattern exists with no other combination of characters.

Answer 1

如果您需要在同一个Regex表达式中包含检查（而不是将两个与and绑定在一起，则可以使用负前瞻：

if (m{/^(?:(?!//).)*class\s{1,10}$className\s{1,10}extends}) {

Answer 2

One solution is to only allow whitespace before the definition (if classes can declared in indented scopes)

/^\s*class\s+<class_name>\s+extends/

Explanation

^ Start of line
\s* 0 or more whitespace characters

Answer 3

I think I found a solution with the help of above comments. I included the below line of code in my code: if(/^\\s*\\/\\/class\\s{1,10}<class_name>\\s{1,10}extends/){next;}

The new piece of code looks like this:

open my $fh, "<", $file_t or die "can't read open '$file_t': $OS_ERROR";        # Opening the file
while (<$fh>) {
if(/^\s*\/\/class\s{1,10}<class_name>\s{1,10}extends/){next;}
elsif(/class\s{1,10}<class_name>\s{1,10}extends/){
    #Perform the operation if we find above pattern
}
close $fh or die "can't read close '$file_t': $OS_ERROR";                      #Closing the file
}

Thanks for the help.