http://example.com/something/XXXXX-some-text.html
-->
http://example.com/something/some-text-XXXXX
where XXXXX is some number between 100 and 100,000

RewriteRule ^(something)/(d{3,6})-([a-zA-Z0-9-]+).html /$1/$3-$2 [R=302,L]

RewriteCond %{REQUEST_URI} !^/something/123-exclude-this.html
RewriteCond %{REQUEST_URI} !^/something/456-and-exclude-this.html
RewriteRule ^(something)/(d{3,6})-([a-zA-Z0-9-]+).html /$1/$3-$2 [R=301,L]

RewriteRule ^(category/subcategory|category/sub/subsub)/(d{3,6})-([a-zA-Z0-9-]+).html /$1/$3-$2 [R=301,L]

RewriteRule ^(.+)/(d{3,6})-([a-zA-Z0-9-]+).html$ /$1/$3-$2 [R=301,L]