Subroutines in Perl - Homonyms
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Don’t give subroutines the same names as built-in functions.

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If you declare a subroutine with the same name as a built-in function, subsequent invocations of that name will still call the builtin...except when occasionally they don’t. For example:  

  sub lock {
      my ($file) = @_;
      return flock $file, LOCK_SH;
  }

  sub link {
      my ($text, $url) = @_;
      return qq{<a href="$url">$text</a>};
  }

  lock($file);                     # Calls 'lock' subroutine; built-in 'lock' hidden
  print link($text, $text_url);    # Calls built-in 'link'; 'link' subroutine hidden

Perl considers some of its builtins (like link) to be “more built-in” than others (likelock), and chooses accordingly whether to call your subroutine of the same name. If the builtin is “strongly built-in”, an ambiguous call will invoke it, in preference to any subroutine of the same name. On the other hand, if the builtin is “weakly built-in”, an ambiguous call will invoke the subroutine of the same name instead.

Even if these subroutines did always work as expected, it’s simply too hard to maintain code where the program-specific subroutines and the language’s keywords overlap:

  sub crypt { return "You're in the tomb of @_\n"    }
  sub map   { return "You have found a map of @_\n"  }
  sub chop  { return "You have chopped @_\n"     }
  sub close { return "The @_ is now closed\n" }
  sub hex   { return "A hex has been cast on @_\n"     }

  print crypt( qw( Vlad Tsepes ) );        # Subroutine or builtin?

  for my $reward (qw( treasure danger) ) {
      print map($reward, 'in', $location); # Subroutine or builtin? 
  }

  print hex('the Demon');                  # Subroutine or builtin? 
  print chop('the Demon');                 # Subroutine or builtin?

There is an inexhaustible supply of subroutine names available; names that are more descriptive and unambiguous. Use them:

  sub in_crypt        { return "You're in the tomb of @_\n"  }
  sub find_map        { return "You have found a map of @_\n"  }
  sub chop_at         { return "You have chopped @_\n"    }
  sub close_the       { return "The @_ is now closed\n"      }
  sub hex_upon        { return "A hex has been cast on @_\n" }

  print in_crypt( qw( Vlad Tsepes ) );

  for my $reward (qw( treasure danger )) {
      print find_map($reward, 'in', $location);
  }

  print hex_upon('the Demon');
  print chop_at('the Demon');

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