If you want to write such a logging function, there is no need to add it manually everywhere. Try just dropping the following at the start of the script:

foreach my $used (keys %main::) {
  no strict;
  if (defined &$used) {
    my $old_sub = \&$used;
    *$used = sub {
      print "Calling $used\n";
      &$old_sub;
    };
  }
}
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This one only abuses subroutines in your main package. Alter as desired. :-)