Question

I am facing problems with Perl string matching/searching using both index as well as the =~ operator. I need to search for the string “RT @zaynmalik: Big cover for @cosmopolitanuk ! Boys looking slick http://example.com/FcWA80HI” in a text file.

if($splitlines[1] =~ /RT @zaynmalik: Big cover for @cosmopolitanuk ! Boys looking slick http://example.com/FcWA80HI/){
     ## Do something ##
}

However, because ‘@‘ is a special character in Perl, I am getting compile errors. Could you suggest me a method to do this? I tried saving the string to a variable like $str, but it did not work (which is understandable).

So, this is what I am doing now,

$max_freq_tweet = 'RT @zaynmalik: Big cover for @cosmopolitanuk ! Boys looking slick http://example.com/FcWA80HI';
if($splitlines[1] =~ /\Q$max_freq_tweet\E/){
    print FILE5 "$splitlines2[1] \n";
}

But it still doesn’t seem to be working.

Answer 1

Either escape the @ via a backslash, or use single quotes.

my $search_string = 'RT @zaynmalik: Big cover for @cosmopolitanuk ! Boys looking slick http://example.com/FcWA80HI';
# or:               "RT \@zaynmalik: Big cover for \@cosmopolitanuk ! Boys looking slick http://example.com/FcWA80HI"

if (-1 != index $str, $search_string) { do something }

If you have a string and want to use it in a regex, you should make sure to protect the meaning via \Q...\E:

if ($str =~ /\Q$search_string\E/) { do something }

This \QUOT\E doesn’t prevent array interpolation, but no character in that string will be considered special; without it the . in the string would match any character!