Well, the error message about being unable to modify <HANDLE> might be considered a bit of a clue: grab the input, and modify it separately:

echo $HOME/Mail/* | perl -e 'while (<STDIN>) { s/sent-mail//; print "$
+_"}'
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Or just use the -p option, and really make it look like your sed command:

echo $HOME/Mail/* | perl -p -e '/sent-mail//'
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update:Whoops. Of course, the missing s before the substitution string was meant as an exercise for the reader ;) echo $HOME/Mail/* | perl -p -e 's/sent-mail//'

But personally, I'd stick with sed, if I've got the choice: it's less memory hungry for such simple tasks