I tried that
var=$g_bin/MISSPIGGY/dc0000.auto_deploy.MISSPIGGY.PRD.cp_austin.20081007122846.26060
perl -pi -e "s/FILENAME/${var}/g" myfile

and am getting the following error:
Bareword found where operator expected at -e line 1, near "s/FILENAME//dbmgtu01"
syntax error at -e line 1, near "s/FILENAME//dbmgtu01"
Execution of -e aborted due to compilation errors.
Any ideals as to why it is not working?