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Perl has a large number of builtin built-in 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 built-in function or keyword.

Noncompliant Code Example

This noncompliant code example codes a subroutine called open(), which clashes with the open() builtin built-in 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 built-in open() rather than the newly crafted subroutine.

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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");

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

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