Here is a one-liner for this:

 perl -p0777 -i.BAK -e 's/my \$t0 = \[gettimeofday\];.+?\.\s*\$1;\s+}/
+/s;' Your.module.names.here
[download]

This takes advantage of the -0 option to set the input record separator to 0x777 (which is not a valid character, and can not occur in your files), and the "s" option in the regex to span matching a '.' across multiple lines.

The explanation in this debian admin article is mostly applicable - except they use the regex option 'm' to handle a slightly different use-case.

If you wanted to match line boundaries, in addition to matching '.' across lines, the 's' and 'm' options can be used together.
Update: Minor Aesthetic change: -iBAK to -i.BAK