and another similar optimization on push, now EQUAL TO RUBY - 357 bytes!!!

sub p{pop@n}sub v{push@n,@_}map{push@L,@C+0;push@C,lc=~/./g}<>;while($
+n<@C){$_=
$C[$n++];if(/n/){$0=0;/-/ or$0=$_+$0*7while($_=index"htaoinse",$C[$n++
+])<7;v$0}
if(/t/){$_=p;$_?$n=$L[$_-1]:last if p}/a/&&v 1+grep$n>$_,@L;if(/h/){$_
+=p;v$n[
$#n-abs];$_>0&&splice@n,@n-2-$_,1}/o/&&print+chr(p);/s/&&v-(p)+p;$0=p,
+$_=p,v
 int$_/$0,$_%$0if/e/;v(($_=getc)?ord:-1)if/i/}
[download]

Thank you!!! What's next?

Well, actually Ruby is 356 bytes (357 minus one backslash), so applying merlyn's hack on last line:

... v+($_=getc)?ord:-1if/i/}

We're back to 356.

/o/&&print+chr(p);
---
/o/&&print+chr p;
[download]

Update: I'm not positive, as I don't know the language, but I think the following can also be done:

$0=p,$_=p,v int$_/$0,$_%$0if/e/;
---
v int($_=p)/($0=p),$_%$0if/e/;
[download]

Saves 2 characters. As I only have one very simple test program, it may not be exercising that spot very well.

** FUNGICIDE **
-- Fungus calendar --
CURTSEY:
        Fungal toe!  Fungal toe!  Fungal hoe!
                -- (Burnt programmer nucleus)
        Ooooooo!
CRUDDY 2nd TOE:
        Nine(!) fungal hyaena toe5!
        Dungy alfalfa, penalty superlunary -- Oh, blubber!
        Ooooooo!
[download]

Update2: With the same caveat ...

/s/&&v-(p)+p;
---
/s/&&v+p-p;
[download]

------
We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.

If you are going to choose where to put your newline then the Ruby is 356:

n=[];p=$<.readlines;f=l=c=0;loop{p[l].downcase.each_byte{|y|f>0?$6?(n<
+<c;c=f=0):
c="htaoins".index(y)+c*7: $1?n<<l+2: $2?n<<STDIN.getc: $3?f=1:(a=n.pop
+;$4?$><<a.
chr: $5?(n<<n[n.size-a.abs-1];a>0?n.delete_at(n.size-a-2):1):(b=n.pop;
+$6?(n<<b/a
;n<<b%a): $7?n<<b-a: b!=0?(l=a-2;break):1))if y.chr=~
"(a)|(i)|(n)|(o)|(h)|(e)|(s)|(t)"};break if(l+=1)>=p.size||l<0}
[download]

... but I'm sure you can find one more byte... Stephen