Insert special text through all regex matches

I have this regex

/<(w+)>(?!w)(?!(</(1)>))/gm

and for instance I have a text like this

RegExr was created by gskinner.com.

Edit the Expression & Text to see matches. Roll over matches or the expression for details. PCRE & JavaScript flavors of RegEx are supported. Validate your expression with Tests mode.

The side bar includes a Cheatsheet, full Reference, and Help. You can also Save & Share with the Community and view patterns you create or favorite in My Patterns.
amir
Explore results with the Tools below. Replace & List output custom results. Details lists capture groups. Explain describes your expression in plain English.
<p>sdf,m.,.msdf</p><p><p><p><p></p>
<b></b>
<p><b><g>
<img>
<br><p><hr>
<p>

all in all ,this regex match with stand alone tag like the last <p>
I want to insert / character before the last character in each matches.
what I want is a match case like <p> becomes </p>