$ cat foo.pl 
#!/usr/bin/env perl
use warnings;
use strict;

sub foo { bar($_[0] x 3)."-".quz(ord($_[0])) }

sub bar { $_[0].length($_[0]) }

sub quz { $_[0].$_[0] }

print foo($_), "\n" for 'a'..'b';

$ perl -MDebug::Trace=foo,bar,quz foo.pl
TRACE:	main::foo("a") called at foo.pl line 11 package main
TRACE:	main::bar("aaa") called at foo.pl line 5 sub main::foo
TRACE:	main::bar() returned: "aaa3"
TRACE:	main::quz(97) called at foo.pl line 5 sub main::foo
TRACE:	main::quz() returned: 9797
TRACE:	main::foo() returned: ("aaa3-9797")
aaa3-9797
TRACE:	main::foo("b") called at foo.pl line 11 package main
TRACE:	main::bar("bbb") called at foo.pl line 5 sub main::foo
TRACE:	main::bar() returned: "bbb3"
TRACE:	main::quz(98) called at foo.pl line 5 sub main::foo
TRACE:	main::quz() returned: 9898
TRACE:	main::foo() returned: ("bbb3-9898")
bbb3-9898