Shell Programming and Scripting

Hi

I want to insert a line after a line by searching for the last occurence for that. I have taken an already posted example.
Say in the following file

a.txt
------
adadfadafadf
adfadadf
cool dfadfadfadfara
adfadfadf
cool aaaaaaaaaaaaaa
hai how are you

I want to insert after the red line. With unix sed command we can do it, but i think it needs an temp file. Using Perl we can do it with out using temp file. Perl onliner perl -i -ne 'print ..................' file name will help.
Can some give me the exact command

Thanks in advance
Lijju Math

something like this

Code:

perl -e 'while(<>) { if ( /cool aaa/ ) { print $_."this is the line\n"; } else { print } }' filename