perl -wMstrict -e
"for my $word (@ARGV) {
  my @bigrams = $word =~ m{ (?= (..) ) }xmsg;
  print qq(bigrams of $word: @bigrams \n)
  }
" foo wibble a be
bigrams of foo: fo oo
bigrams of wibble: wi ib bb bl le
bigrams of a:
bigrams of be: be