As for Carp, it's scope is limited to the conditional block.

In my understanding, imported function names are available throughout the package into which they are imported.

>perl -wMstrict -le
"{ package Foo;
   cluck('1st cluck in ', __PACKAGE__);
   }
 ;
 print 'in ', __PACKAGE__;
 ;
 { package Foo;
   if (0) { use Carp qw(cluck); }
   cluck('2nd cluck in ', __PACKAGE__);
   }
 ;
 print 'again in ', __PACKAGE__;
 cluck('clucking in ', __PACKAGE__) if defined &cluck;
 ;
 { package Foo;
   cluck('3rd cluck in ', __PACKAGE__);
   }
"
1st cluck in Foo at -e line 1
in main
2nd cluck in Foo at -e line 1
again in main
3rd cluck in Foo at -e line 1
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