in reply to command lineIn place edit with a filter

Assuming you get the full file name ...
dir /b/S *.dsp | perl -e 'BEGIN{@ARGV=map{ chomp and $_ }<ARGV>}' \ -i.bak -pe "s#\bGPP\b#Arjun#i;"
No longer a oneliner, but it should do the job.
HTH

_________
broquaint