Yes, it has to be imported from another package to override. That's what subs is for. 

$ perl -e'
   sub readpipe { die };
   readpipe("ls");
'

$ perl -e'
   use subs qw( readpipe );
   sub readpipe { die }
   readpipe("ls");
'
Died at -e line 3.

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In reply to Re: Overriding built-in function works only via import()? by ikegami
in thread Overriding built-in function works only via import()? by perlancar

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