how about changing assignment to:

$engine = sprintf(%02d,$1);
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to make "00" which is true, rather than "0" which isn't, in cases where $1 = 0.

Seekers of truth must know thy path...

what is truth? (Camel 2, page 20)

• any string is true except for "" and "0"
• any number is true except for 0
• any reference is true
• any undefined value is false

So as long as you test "00" in a string rather than numerical context, you should be OK.

cLive ;-)

Update: after a minute's thought, I changed the line to sprintf to the assignment...