in reply to Working with BIG binary fields

I don't understand the format of the data you've posted. But, assuming that by "binary", you really do mean binary, and not some ascii-encoded hex representation of the original binary, then the solution to your problem is vec. 

my $binaryString = ...;

if( vec( $binaryString, 123, 1 ) == 1 ) {
    ## bit 123 was set
}
else {
    ## it wasn't
}

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