Escaping Perl 正则表达式中的特殊字符

Question

I'm trying to match a regular expression in Perl. My code looks like the following:

my $source = "Hello_[version]; Goodbye_[version]";
my $pattern = "Hello_[version]";
if ($source =~ m/$pattern/) {
  print "Match found!"
}

The problem arises in that brackets indicate a character class (or so I read) when Perl tries to match the regex, and the match ends up failing. I know that I can escape the brackets with \[ or \] , but that would require another block of code to go through the string and search for the brackets. Is there a way to have the brackets automatically ignored without escaping them individually?

Quick note: I can't just add the backslash, as this is just an example. In my real code, $source and $pattern are both coming from outside the Perl code (either URIEncoded or from a file).

Answer 1

\\Q will disable metacharacters until \\E is found or the end of the pattern.

my $source = "Hello_[version]; Goodbye_[version]";
my $pattern = "Hello_[version]";
if ($source =~ m/\Q$pattern/) {
  print "Match found!"
}

http://www.anaesthetist.com/mnm/perl/Findex.htm

Answer 2

Use quotemeta() :

my $source = "Hello_[version]; Goodbye_[version]";
my $pattern = quotemeta("Hello_[version]");
if ($source =~ m/$pattern/) {
  print "Match found!"
}

Answer 3

You are using the Wrong Tool for the job.

You do not have a pattern! There are NO regex characters in $pattern!

You have a literal string.

index() is for working with literal strings...

my $source = "Hello_[version]; Goodbye_[version]";
my $pattern = "Hello_[version]";
if ( index($source, $pattern) != -1 ) {
    print "Match found!";
}

Answer 4

You can escape set of special characters in an expression by using the following command.

expression1 = 'text with special characters like $ % ( )';

expression1 =~s/[\\?*+\\^\\$[]\\(){}\\|-]/"\\$&"/eg ;

This will escape all the special characters

print "expression1'; # text with special characters like \\$ \\% ( )

Answer 5

Quoting a $pattern defeats the purpose of Regular Expressions unless its being used as a known literal and being dumped into a real regex.

edit
Otherwise, just use index() to find the position of the substring. With that information just use substr() to extract surrounding data if necessary.