Sometimes re debug can help:

#!/usr/bin/perl

use strict;
use warnings;
use re 'debug';

m#/([^/]*)$#;
     
neil@neptune ~/src/perltest $ ./redebug.pl 
Compiling REx "/([^/]*)$"
Final program:
   1: EXACT </> (3)
   3: OPEN1 (5)
   5:   STAR (17)
   6:     ANYOF[^/][{above_bitmap_all}] (0)
  17: CLOSE1 (19)
  19: SEOL (20)
  20: END (0)
anchored "/" at 0 floating ""$ at 1..9223372036854775807 (checking anc
+hored) minlen 1 
Use of uninitialized value $_ in pattern match (m//) at ./redebug.pl l
+ine 7.
Freeing REx: "/([^/]*)$"
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