UNIX for Dummies Questions & Answers

i have following in block

if [ `expr substr "$line_by_line" 1 13` == "0000000000000" -o `expr substr "$line_by_line" 26 12` == "UA ITEM FROM" ]
then
echo "Exclusion criteria"
else
echo "Not exclusion criteria"
fi

now above block runs fine if value of variable line_by_line is "00000000dfahfahfahfahsfhasfhafhahfahfahf" but same block gives error if value is "0000000000202000501000069BAG ICE 000008840"
error is
test_script.sh: line 4: [: too many arguments

Only diff I can see is in second condition of If statement.....for second value spaces are coming.....

Any inputs......to this strange problem

I guess problem is coming because of default value of IFS variable...
When I set that to new variable the code is working fine