perl -MYAPE::Regex::Explain -le 'print YAPE::Regex::Explain->new( qr/([^>]\d+[a-z]*[^<])/ )->explain'
The regular expression:

(?-imsx:([^>]\d+[a-z]*[^<]))

matches as follows:
  
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    [^>]                     any character except: '>'
----------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
    [a-z]*                   any character of: 'a' to 'z' (0 or more
                             times (matching the most amount
                             possible))
----------------------------------------------------------------------
    [^<]                     any character except: '<'
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------