As long as freetype-config is in the PATH, you should be able to just re-run the installation.
If you have previously installed Imager you could:
but this will install even if Imager fails tests.
To avoid that:
cpan> look Imager
$ perl Makefile.PL
done.
gif: includes found - libraries found
ungif: includes found - libraries found
jpeg: includes found - libraries found
png: includes found - libraries found
tiff: includes found - libraries found
freetype2: configured via freetype-config
T1-fonts: includes found - libraries found
TT-fonts: includes found - libraries found
w32: includes not found - libraries not found
...
$ make
$ make test
$ sudo make install
means it found your freetype 2 installation successfully.