When you want to replace all occurrences of a single character with a different single character, use tr/// instead of s///g. It is faster, and you won't ever be bitten by the meta-character problem, because tr/// does not respect meta-characters (no interpolation). Your documentative use of $rem and $rep would need to be replaced by a comment, of course.

# Translate all '|' (pipe) characters into ' ' (spaces).
while (<FILE>) {
  tr/|/ /;
  print OUTP;
}
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tr/// is in the perlop manpage. It does a lot more that just single/single transliteration, but this is where tr/// and s/// overlap in function.

FYI, you can do the equivalent under Windows with this one-liner:
perl -pe "tr/|/ /" filename > c:\joshperl\deptemp.txt