C:\test>type junk.dat
        A       B       C       D       E
A       1       1       1       1       1
B       1       1       1       1       1
C       1       1       1       1       1
D       1       1       1       1       1
E       1       1       1       1       1

C:\test>perl -plae" $.== 1 and $F[0] eq 'A' and $_ = 'ID' . $_" junk.dat
ID      A       B       C       D       E
A       1       1       1       1       1
B       1       1       1       1       1
C       1       1       1       1       1
D       1       1       1       1       1
E       1       1       1       1       1