# No worries about line breaks
perl -i -pe's/Will Emigh/YAPH Emigh/g' 

# line breaks concern me but STDOUT will do
perl -pe'$a.=$_}{$_=$a;s/Will(\n*) (\n*)Emigh/YAPH\1 \2Emigh/g'

# line break concern me and lets put it back in the file
perl -ne'BEGIN{$f=$ARGV[0]}$a.=$_}{$_=$a;s/Will(\n*) (\n*)Emigh/YAPH\1 \2Emigh/g;open F,">$f";print F $_'