I got this from a guru pal. Though once you see it, it seems simple; and I don't doubt TIMTOWTDI. It stores the 'stat's of each file in the BEGIN block and restores them in the END block. As a Perl success story: a very slightly tweaked version (with a more elaborate substitution) did a job at work that our Windows NT contractor quoted us $15,000 to do. Viva la Perl.

perl -pi -e 'BEGIN { %s = map { $_ => [stat $_] } @ARGV} s/foo/bar/g; 
+END { for $f (keys %s) { utime(@{ $s{$f} }[8,9], $f) } }' [files]
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