binding operator

[catfish1116]

I have written some code 2 ways, (shown below). The firsts one without the binding operator does work. The second one, with the binding operator doesn't work.

   print "Enter a string: ";
   chomp(my $_ = <STDIN>);

   if ($_ = /(a|b|x)/i) {
     print "Its a good match\n";
   } else {
     print "That was not a good match\n";
   }


  print "Enter a string: ";
   chomp(my $teststring = <STDIN>);

   if ($teststring =~ m{ /(a|b|x)/}i) {
     print "Its a good match\n";
   } else {
     print "That was not a good match\n";
   }

I guess I don't understand the difference between binding and non-binding reg-exps. TIA, The Catfish

[choroba]

The regexes aren't the same:

$ perl -wE 'say for qr/(a|b|x)/i, qr{ /(a|b|x)/}i'
(?^ui:(a|b|x))
(?^ui: /(a|b|x)/)

Moreover, $_ = /.../ not only matches against $_, but also changes its content (it sets it to the result of the match).

Also note that my $_ is invalid since 5.24.

[Fletch]

Well for one thing your first version is assigning the result of comparing qr/(a|b|x)/i against $_ back into $_. Harmless in this case, but . . .

For another, your second chunk is attempting to match the regex qr{ /(a|b|x)/} against $teststring which isn't what you mean either. When you use the match operator with different delimiters you don't need the extra slashes (e.g. you really meant if( $teststring =~ m{(a|b|x)}i ) {...} there).

[Anonymous Monk]

Also: I don't think that you can say: my $_. That's a special Perl predefined name ... which I don't recommend that you use. Use my to create a local variable-name as you did in the second case.

[Anonymous Monk]

$_ is a special Perl predefined name ... which I don't recommend that you use

Your recommendations mean nothing. Using $_ is best practice, in most situations.