It looks like plenty of programs support the document format from Corel WordPerfect and as such can be used to re-save the document to the open source ODF text document format (*.odt). Not all formatting may be properly saved though.
Convert Corel WordPerfect document file to ODF text document.
We have found 7 software records in our database eligible for .wpd to .odt file format conversion.
Microsoft Windows software - convert wpd to odt on Windows
A free word processing program, part of GNOME office productivity bundle
Convert from wpd file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned wpd to odt. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
One of the most popular word processor program from Microsoft Office suite
Apple macOS / Mac OS X software - convert wpd to odt on OS X
A Mac version of the Abiword word processor
Linux/Unix software - convert wpd to odt on Linux
A Linux version of the Abiword word processor
An open source word processor for Linux
Multiplatform software - convert wpd to odt on any platform
Word processor and text editor from OpenOffice.org suite
Full-featured word processing and desktop publishing tool from LibreOffice suite