DCL31-PL. Do not overload reserved keywords or subroutines

Perl has a large number of builtin functions, they are described on the perlfunc manpage [Wall 2011]. Perl also has a handful of reserved keywords such as while; they are described on the perlsyn manpage [Wall 2011].

Do not use an identifier for a subroutine that has been reserved for a builtin function or keyword.

Noncompliant Code Example

This noncompliant code example codes a subroutine called open(), which clashes with the open() builtin function.

sub open {
  my ($arg1, $arg2, $arg3) = @_;
  print "arg1 = $arg1\n";
  print "arg2 = $arg2\n";
  print "arg3 = $arg3\n";
}

open( FOO, "<", "foo.txt");     # What does this do?

Perl (v5.12.1) actually invokes the builtin open() rather than the newly crafted subroutine.

Compliant Solution

This compliant solution uses a different name for its subroutine; consequently it behaves as expected.

sub my_open {
  my ($arg1, $arg2, $arg3) = @_;
  print "arg1 = $arg1\n";
  print "arg2 = $arg2\n";
  print "arg3 = $arg3\n";
}

my_open( FOO, "<", "foo.txt");

Exceptions

DCL31-EX0: This rule does not apply to object methods. Object methods are easy for the parser to distinguish from builtin functions or keywords due to their distinct syntax.