C:\>perl -anF/,/ -e "print qq($F[0]\n)" file1.txt>c:\file1a.txt
C:\>type 1a.txt
a
b
d
c
e
C:\>perl -anF/,/ -e "print qq($F[0]\n)" file2.txt>file2a.txt
C:\>type 2a.txt
a
b
c
d
c
e
C:\>diff file1a.txt file2a.txt
4d3
<c