$ perl -We '$_="I have 10+4 dollars.\n"; s/(10\+4)/$1/; print;'
I have 10+4 dollars.
$ perl -We '$_="I have 10+4 dollars.\n"; s/(10\+4)/$1/e; print;'
I have 10+4 dollars.
$ perl -We '$_="I have 10+4 dollars.\n"; s/(10\+4)/$1/ee; print;'
I have 14 dollars.