$ cat foo.txt
  indented

not indented
  bla
bla
  bla

not indented
  yak

##</code><code>##

$ perl -Mstrict -wE '$/="";while (<>) { chomp; if (/^\w/ .. /^$/) {print; exit} }' < foo.txt
not indented
  bla
bla
  bla