Substring position

#! /bin/bash
#  Add file to the /Syncs Git Repository
#  Run cmd: bash /Scripts/Git/git-adddbox.sh

fstfilt=".dropbox"
secfilt=".git"
trdfilt=".kde"
dboxsrc="/home/files/dbox_dump.txt"
dboxout="/home/files/dbox_redump.txt"
curdir=$PWD;
echo "Working Dir => '$curdir'";
cd /Syncs;
git init;
git config user.name "$USER";
git config user.email "tbotnik@gmail.com"
git branch 'Syncs';
git checkout 'Syncs';

while IFS= read -r line
do
    dtmp=${line%%$fstfilt}
    gtmp=${line%%$secfilt}
    ttmp=${line%%$trdfilt}
    dpos=${#dtmp}
    gpos=${#gtmp}
    tpos=${#ttmp}
    echo $dpos $gpos $tpos $line
    if [[ $dpos -eq 0 && $gpos -eq 0  && $tpos -eq 0 ]]; then
        echo $dpos $gpos $tpos $line
#   else
#       git add $line
    fi
done < "$dboxsrc"
cd $curdir;

Lines 21-26 do not process correctly according to BASH tutorials, which say they will give the position of the substring in the "linw" variable. I need a surefire way to get the substring position.

Wondering if instead of:

fstfilt=".dropbox"
secfilt=".git"
trdfilt=".kde"

I really need:

fstfilt="\.dropbox"
secfilt="\.git"
trdfilt="\.kde"