/               Match a literal '/' character

    (               The start of a capturing block ($1)

      .+?             Match any character (except newline), one-or-more times (as few as possible)

    )               The end of $1

    $               Match only if at end of string (or final newline)





....

 $1 = 'sham/b'




   Back-tracked within regex and rematched
   |
   VVV
//(.+?)$/


           |
           V
'ro/sham/bo'
    ^^^^^^^

[Visual of regex at 'rxrx' line 0]         [step: 35]

#######


 $1 = 'sham/bo'




      End of $1
      |
      V
//(.+?)$/


           |
           V
'ro/sham/bo'
    \_____/

[Visual of regex at 'rxrx' line 0]         [step: 36]


#######

 $1 = 'sham/bo'




       Testing if at end of string (or final newline)
       |
       V
//(.+?)$/


           |
           V
'ro/sham/bo'


[Visual of regex at 'rxrx' line 0]         [step: 37]



#######





 $1 = 'sham/bo'




       Assertion satisfied
       |
       V
//(.+?)$/


           |
           V
'ro/sham/bo'


[Visual of regex at 'rxrx' line 0]         [step: 38]




#######


 $1 = 'sham/bo'




        Regex matched in 39 steps
        |
        V
//(.+?)$/


           |
           V
'ro/sham/bo'


[Visual of regex at 'rxrx' line 0]         [step: 39]