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The binding operator - er - binds an operation to be performed to a particular variable instead of $_. I did find this rather confusing at the beginning, because I used to read this as some kind of assignment. See this as if you're assigning "an operation" to the variable.

As for the use of $_[0], Perl passes variables by reference instead of value, which means that you can modify (if possible) the actual variables that are passed to a function. Thus:

sub double_it { $_[0] *= 2; } my $x = 1; print "\$x is $x\n"; double_it($x); print "\$x now is $x\n";
will multiply $x by two, ending up with the following output:
$x is 1 $x now is 2
The piece of code you proposed seems some implementation of a templating system; each substitution command replaces occurrences of some placeholder (like %HTTP_HOST%) with the value given by a call to the handleEnvVariable sub with the given parameter (a call to a function is allowed inside the substitution part due to the "e" modifier).

Flavio (perl -e "print(scalar(reverse('ti.xittelop@oivalf')))")

Don't fool yourself.

In reply to Re: What are multiple $_[0] =~ operations doing? by polettix
in thread What are multiple $_[0] =~ operations doing? by Plotinus

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