if (substr($acct_trtmt_hsty,1,1) =~ m/([789])/) {
    print "the number is: " . $1;
  }

##</code><code>##

  my @numbers = $acct_trtmt_hsty =~ m/'([789])'/g;
  print join ":", @numbers;

##</code><code>##

$acct_trtmt_hsty, =~ s/(')([789])(')/$1 . ($2-4) . $3/eg;   # note: many different ways to write this regex