Try this:

perl -ne 'print unless /\x1a/;' concatfile >x.txt
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Update: This only works if the \x1a is on a line by itself. If not, try this:

perl -npe 's/\x1a//;' concatfile >x.txt
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This is however virtually the same thing as yours. It works for me on a file with random \x1a scattered throughout it (as does your code if I drop the binmode. If you're on Unix, you don't need it, and you would need to put it after the open of concatfile for it to work as well).

CU
Robartes-