Learning Perl: 8.4. The Binding Operator, =~

@H_502_6@

 

@H_502_6@

8.4. The Binding Operator,=~ Matching against $_ is merely the default; the binding operator (=~) tells Perl to match the pattern on the right against the string on the left,instead of matching against $_.[ ] For example: [ ] The binding operator is used with some other operations besides the pattern match,as you'll see later. my $some_other = "I dream of betty rubble."; if ($some_other =~ //brub/) { print "Aye,there's the rub./n"; }@H_502_45@ The first time you see it,the binding operator looks like some kind of assignment operator,but it's not. It is saying,"This pattern match that would attach to $_ by defaultmake it work with this string on the left instead." If there's no binding operator,the expression is using $_ by default. In the (somewhat unusual) example below,$likes_perl is set to a Boolean value according to what the user typed at the prompt. This is a little on the quick-and-dirty side because the line of input itself is discarded. This code reads the line of input,tests that string against the pattern,and discards the line of input.[*] It doesn't use or change $_ at all. [*] The line of input is not automatically stored into $_ unless the line-input operator (<STDIN>) is alone in the conditional expression of a while loop. print "Do you like Perl? "; my $likes_perl = (<STDIN> =~ //byes/b/i); ... # Time passes... if ($likes_perl) { print "You said earlier that you like Perl,so.../n"; ... }@H_502_45@ Because the binding operator has fairly high precedence,the parentheses around the pattern-test expression aren't required,so the following line does the same thing as the one aboveit stores the result of the test (and not the line of input) into the variable: my $likes_perl = <STDIN> =~ //byes/b/i;@H_502_45@

@H_502_6@