Code Golf: Finite-state machine!

Answer 1

Perl — 184 characters

(Count excluding all newlines, which are optional.)

($s)=split' ',<>;$\=$/;
while(<>){chomp;$r{$_[1].$_[0]}=$_[2]if split>2;$t=$_}
$_=$t;
1 while$s&&s/(.)(.*)/print"$s $1",($s=$r{$1.$s})?" -> $s":"";$2/e;
print$s=~/^[A-Z]/?"ACCEPT":"REJECT"

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Also, this 155-character program does not implement the intermediate outputs, but executes the machine entirely as a repeated substitution on the whole FSM definition (changing the start state and input string). It was inspired by, but not derived from, the sed solution. It could be shortened by 2 characters by converting the (?:...) into a (...) and renumbering as needed.

$/="";$_=<>;
1 while s/\A(\S+)(?: +\S+)*\n(.*\n)?\1 +(.) +(.+)\n(.*\n)?\3([^\n]*)\n\z/$4\n$2$1 $3 $4\n$5$6\n/s;
print/\A[A-Z].*\n\n\z/s?"ACCEPT\n":"REJECT\n"