perl -MO=Xref mytest.pl File mytest.pl Subroutine (definitions) Package Internals &SvREADONLY s0 &SvREFCNT s0 &V s0 &getcwd s0 &hv_clear_placeholders s0 Package PerlIO &get_layers s0 Package Regexp &DESTROY s2147483647 Package Tie::Hash::NamedCapture &CLEAR s0 &DELETE s0 &EXISTS s0 &FETCH s0 &FIRSTKEY s0 &NEXTKEY s0 &SCALAR s0 &STORE s0 &TIEHASH s0 &_tie_it s0 &flags s0 Package UNIVERSAL &DOES s0 &VERSION s0 &can s0 &isa s0 Package constant &_make_const s0 Package main &fizzbuzz s3 Package mro &method_changed_in s0 Package re &is_regexp s0 ®exp_pattern s0 ®name s0 ®names s0 ®names_count s0 Package version &("" s0 &() s0 &(* s0 &(*= s0 &(+ s0 &(+= s0 &(- s0 &(-= s0 &(/ s0 &(/= s0 &(0+ s0 &(<=> s0 &(abs s0 &(bool s0 &(cmp s0 &(nomethod s0 &_VERSION s0 &boolean s0 &declare s0 &is_alpha s0 &is_qv s0 &new s0 &noop s0 &normal s0 &numify s0 &parse s0 &qv s0 &stringify s0 &vcmp s0 Subroutine (main) Package (lexical) $fb i3, 4 @$fb 4 Package main $_ 4 &fizzbuzz &3 Subroutine fizzbuzz Package (lexical) $line i10, 13 $m i7, 9 $n i7, 9 $num 11, 12, 13 @out i8, 13, 15 mytest.pl syntax OK