$ PERL_CORE=1 tusc ./perl ext/Storable/t/weak.t | grep Util

##</code><code>##

stat64("./Scalar/Util.pmc", 0x7fffdf30) ............. ... ERR#2 ENOENT
stat64("./Scalar/Util.pm", 0x7fffdeb0) .............. ... ERR#2 ENOENT
stat64("../lib/Scalar/Util.pmc", 0x7fffdf30) ........ ... ERR#2 ENOENT
stat64("../lib/Scalar/Util.pm", 0x7fffdeb0) ......... ... = 0
open("../lib/Scalar/Util.pm", O_RDONLY|0x800, 0666) . ... = 4
stat64("./List/Util.pmc", 0x7fffdf30) ............... ... ERR#2 ENOENT
stat64("./List/Util.pm", 0x7fffdeb0) ................ ... ERR#2 ENOENT
stat64("../lib/List/Util.pmc", 0x7fffdf30) .......... ... ERR#2 ENOENT
stat64("../lib/List/Util.pm", 0x7fffdeb0) ........... ... = 0
open("../lib/List/Util.pm", O_RDONLY|0x800, 0666) ... ... = 4
stat64("../lib/auto/List/Util/Util.so", 0x40011090) . ... = 0
stat64("../lib/auto/List/Util/Util.bs", 0x40011090) . ... = 0
open("../lib/auto/List/Util/Util.so", O_RDONLY, 0) .. ... = 4
open("../lib/auto/List/Util/Util.so", O_RDONLY, 0) .. ... = 4

##</code><code>##

$ PERL_CORE=1 ./perl ext/Storable/t/weak.t

##</code><code>##

$ tusc ./perl -I./lib -MScalar::Util=weaken -e1 | grep Util

##</code><code>##

$ nm ./lib/auto/List/Util/Util.so | grep weak                                                    
[77]     |            0|       0|FUNC |GLOB |0|   UNDEF|Perl_sv_rvweaken
[102]    |     67145504|     384|FUNC |GLOB |0|   .text|XS_Scalar__Util_isweak
[66]     |     67145184|     288|FUNC |GLOB |0|   .text|XS_Scalar__Util_weaken

##</code><code>##

$ find /opt/perl* -path "*bin/perl"

$ find /opt/perl* -path "*bin/perl" -exec {} -v \; | grep 'is perl'