The plug-in does not search and replace.
When making a high quality voice recording, (for example, an audiobook), there are often unwanted clicks and noises in spaces between words that can be distracting to the listener. One option would be to silence the gaps between words using the "Silence Audio (Ctrl+L)" command. However, silencing the audio completely can sound weird and distracting, particularly when listening with headphones. A better solution (as recommended by one of the ACX tutorials), is to replace gaps that contain clicks or other noises with "room tone".
"Room tone" refers to the "almost silent" background noise that is present throughout the recording.
To manually replace the audio in a gap between words with "room tone", you would select a short section of "room tone" from the recording that is the same length as the audio that you wish to replace, copy it, noting the exact length, then select exactly the same length within the noisy gap, and paste the room tone into that selection. This is fiddly and time consuming to do because the copied audio must be the exact same length as the audio that you wish to replace, otherwise the spacing between words will change.
How this plug-in helps, is that the copied "room tone" does not need to be the same length as the audio that you wish to replace.
If the copied audio is longer than the selection into which you are pasting, then "Punch Paste" will use just enough of the copied audio as is required to fill the selection.
If the copied audio is shorter than the selection into which you are pasting, then "Punch Paste" will repeat the copied audio as many times as required to fill the selection.
In both cases, the length of the selection into which you are pasting remains the same length after pasting as it was before pasting.