open(FH,shift) or die "cannot read file: $!";read FH, $b, 1<<12;

Why did you choose such an enormously long name for your filehandle? ;-)

If you are really going for shortness though, you can still skip read() and set $/ to a reference. Granted that error handling isn't equivalent, but the following should do for use in a one-liner:

$/=\4096;$b=<>;
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-sauoq
"My two cents aren't worth a dime.";