I'm not sure what you gain by including code when the debugger already does this...

If you set the frame option in the debugger, it'll tell you when you enter a subroutine:
PERLDB_OPTS="frame=1" perl -d myprogram.pl
If you just want a trace (and don't need to debug interactively), you can use the NonStop option:
 PERLDB_OPTS="NonStop frame=1" perl -d myprogram

The output with NonStop on (with interspersed program output) looks like this:

Package pathdiff.pl.
entering Algorithm::Diff::traverse_sequences
 entering Algorithm::Diff::_longestCommonSubsequence
  entering CODE(0x80fdd48)
  entering CODE(0x80fdd48)
  entering CODE(0x80fdd48)
  entering Algorithm::Diff::_withPositionsOfInInterval
   entering CODE(0x80fdcb8)
  entering CODE(0x80fdcb8)
 entering main::match
same:   a       a
 entering main::discA
omitA:  b
 entering main::discB
omitB:          c
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Updated: added output sample