Make a perl script (yourscript.pl) that contains the line:

s/[\n\r\f]//g
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Then run:

perl -i.tmp -p yourscript.pl file.txt
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against your file...say file.txt.
That is how you edit a file in-place. You will have your old file as file.txt.tmp to do a comparison and confirm it worked if you want.
You could also do this for each line if you read the file into an array.
That is...

open (F,"file.txt");
@ar = <F>;
close(F);
foreach (@ar) {
    s/[\n\r\f]//g;
    # do what you want with the line.
}
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Update:
Well, it seems I was a little slow on the typing, other than the other posts do not contain the '\f'. You may have wanted to include this as a reply on your last post cuz now that one is going to get unneeded attention.