Here's another regex-based solution: 

$string = '4B';

($out = $string) =~ s/(.)/unpack 'B8', $1/eg;

[download]

Fairly straightforward, actually - this globally (/g) matches every character ((.)), executes (/e) the embedded snippet of code, and replaces the matched character with the result of the call to unpack.

EDIT: please see below for a version that actually works properly.

In reply to Re: Convert ASCII string to 7-bit binary string by AppleFritter
in thread Convert ASCII string to 7-bit binary string by Pascal666

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