stringperlconditional-operator

What does perl substitution operator return when applied to a string?

I can't understand what does the perl substitution return after applied. I have the following snippet

my $w = "-foo";  
my $v = $w =~ s/-//?0:1;  
print "---- $v\n";

If $w is -foo, this prints ---- 0, but if $w is foo, this prints ---- 1

Why does it behave like that?

Solution

  • You have reversed the logic in your code

    my $v = $w =~ s/-// ? 0 : 1;

    As Gilles notes in the comments, this is the operation of the ternary/conditional operator:

    condition ? caseTrue : caseFalse

    The conditional operator will have its condition evaluate to "true" when the pattern matches, and the value for true that you have put in is 0. So you have reversed the logic:

    "Return 0 for true, and 1 for false".

    The true result of the operator can be demonstrated if you simply remove the ternary, then it will print 1.