It's natural that you want to use uc like that.

First method - Call some methods on native types

You can use autobox for this in the following manner:

  2 package MyArray;
  3 use base qw(autobox);
  4 sub uc { return map { uc } @{$_[0]};   };
  5
  6
  7 package MyString;
  8 use base qw(autobox);
  9
 10 sub split { [ split $_[1], $_[0] ] ; };
 11
 12
 13 package main;
 14
 15
 16 use autobox ARRAY => 'MyArray';
 17 use autobox STRING => 'MyString';
 18 use feature 'say';
 19
 20 say "one:two:three:four"->split(':')->uc();
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or shorter:

  1
  2 use feature 'say';
  3 use autobox ;
  4
  5 sub ARRAY::uc { return map { uc } @{$_[0]};   };
  6 sub SCALAR::split { [ split $_[1], $_[0] ] ; };
  7
  8
  9 say "one:two:three:four"->split(':')->uc();
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Second method - Overriding the CORE method uc

This is simple , you just make up your own new method and you replace the one from CORE with your own in the BEGIN block

  1
  2
  3 use feature 'say';
  4
  5 sub new_uc {
  6     @_ > 1
  7     ? map { uc } @_
  8     : uc $_[0] ;
  9 }
 10
 11 BEGIN {
 12     *CORE::GLOBAL::uc = *new_uc;
 13 }
 14
 15 say uc split(':',"one:two:three:four");
 16
 17 my $w = uc "a";
 18 say $w;
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By writing new_uc like that you assure that it will work as the old uc for scalars and in the new way for arrays

P.S. : There would be a third method .. to get into the Perl C sources in file pp.c at line 3620 and modify PP(pp_uc) so that it will behave as it should. Unfortunately that would require also reading av.c to understand how the arrays work , and reading or guessing what all of the macros do. Btw , has anyone else tried this before ? How in God's name do you start understanding those sources ?