Sidestepping the wisdom of time based loops.....

Your $start assignment is unnecessary. The special $^T variable already contains that information. (i.e. perl stores the time() value at startup in $^T) So, you could rewrite the above as:

while ( time-$^T <= 7200 ) {
  ....sutff....
}
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Note: this is a mod_perl gotcha since the "startup" time could be a looong time ago. $^T is also the value used when the -M, -A, and -C filetest operators determine the relative age of a file. The age is relative to whatever happens to be in $^T, which has implications for any long running perl program.

-Blake