m/(?x)
  ((?:blah){3})   ## match w/ capture: blahblahblah
/
##</code><code>##

... =~ m/(?x) 
  \A
  ## match w/ capture: one or more alpha, punct, or space posix characters
  ( [[:alpha:][:punct:][:space:]]+ )
  \z
/;

## and 

... =~ m/(?x)
  \A
  ## match w/capture: one or more alpha posix characters
  ( [[:alpha:]]+ )
  \z
/;

##</code><code>##

.