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Wiki MarkupPerl has a large number of builtin functions, they are described on the {{perlfunc}} manpage \[[Wall 2011|AA. Bibliography#Manpages]\]. Perl also has a handful of reserved keywords such as {{while}}; they are described on the {{perlsyn}} manpage \[[Wall 2011|AA. Bibliography#Manpages]\of 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( my FOO$input, "<", "foo.txt");     # What does this do?

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

...

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( my FOO$input, "<", "foo.txt");

Exceptions

DCL31-PL-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 because of their distinct syntax.

Related Guidelines

CERT C++ Secure Coding Standard: DCL32-CPP. Do not declare or define a reserved identifier
CERT C Secure Coding Standard: DCL37-C. Do not declare or define a reserved identifier

Risk Assessment

Using reserved keywords can lead to unexpected program behavior and surprising results.

Automated Detection

Bibliography

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Related Guidelines

Bibliography

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Image AddedImage AddedImage Added|http://search.cpan.org/dist/Perl-Critic/lib/Perl/Critic/Policy/Subroutines/ProhibitBuiltinHomonyms.pm] \[[Wall 2011|AA. Bibliography#Manpages]\] [perlfunc|http://perldoc.perl.org/perlfunc.html], [perlsyn|http://perldoc.perl.org/perlsyn.html] EXP11-C. Do not apply operators expecting one type to data of an incompatible type      03. Expressions (EXP)      EXP13-C. Treat relational and equality operators as if they were nonassociative