One common form of human readable text is like: 01:23:45:67:89:AB. In a binary form, that is 6, eight bit bytes (2 hex digits each) or 48 bits or 3, 16 bit unsigned integers. If that human form is stored as a string for easy output to humans, that's 17 bytes of ASCII plus probably a trailing zero. A binary file would typically just store the 48 bits (not a string).

You can use regex to replace one binary string with another binary string. However, I am not sure that is best here because we have almost no application details. I suspect that more code than just one regex will be required for a good UI - could be wrong about that - perhaps depends upon what is meant by "good UI"! There are also other possibilities in the menagerie of Perl options.

I hope the OP can show at least a partial hex dump of the file and then explain what he wants to replace with what.
And comment about potential CRC characters is spot on- probably don't exist, but they might.

I would be curious to know a bit higher level of the app like why a low level binary edit is needed?