Hey!

% which touch
/usr/bin/touch
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Portability counts! You should make it more robust. Maybe with env...

`echo "#!/usr/bin/env touch $file" > tmp.sh`;
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Of course, that's slower at runtime. Extra forks and all. Maybe precalculate it...

`echo "#!\$(which touch) $file" > tmp.sh`;
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But really, sh is pretty weak. And we've already got perl anyway, right? So why not use it to its fullest incapacity?

`echo "#!/usr/bin/env perl -e 'system \"\$(which touch) $file\"'" > tm
+p.pl`;
system './tmp.pl';
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Of course, that's getting pretty silly. And tedious. Obviously a little metaprogramming is called for to generate those expressions...