pgpewrap is a program that is part of the Mutt email client package. It is pretty badly documented, not having a manpage or accepting "--help" or "-h" arguments. It has a brief mention in the PGP-Notes.txt file in the mutt documentation:

This is a little C program which does some command line munging: The first argument is a command to be executed. When pgpewrap encounters a "--" (dash-dash) argument, it will interpret the next argument as a prefix which is put in front of all following arguments.

Example:

pgpewrap pgpe file -- -r a b c

will execute:

pgpe file -r a -r b -r c

This script is needed with PGP 5 and with GPG, since their command line interfaces can't be properly served by mutt's format mechanism.

The reason you might need to use this is because GPG requires multiple recipients to be listed with a "-r" each, such as "-r key1 -r key2 -r key3" while mutt outputs multiple recipients as a list, such as "-r key1 key2 key3". pgpewrap is used to change mutt's output before executing gpg.