There is an option to build the regex tester included in the tqt3/examples/regexptester directory.

The patch is to expand the 'Match' row vertically to enable multiline matches to be viewed.

Use the command line option 'build_regextester' to include the regextester build:

build_regextester=y ./BUILD-TDE.sh	to build unpatched
build_regextester=p ./BUILD-TDE.sh	to build with the patch

It will be installed to the TDE binary directory as 'regextester'.

   "A Small Application for Testing Regular Expressions

    Regular expressions can sometimes be tricky to get right,
    especially those that use the * quantifier. This application lets
    you type in a regexp (without doubling the backslashes) and some
    test text, and to execute the regexp and see the results. If you
    click the Copy button the regexp will be copied to the clipboard
    (with the backslashes doubled, ready for you to paste into your
    program). Previous regexps and test texts are remembered
    throughout the session and can be accessed by dropping down the
    comboboxes."

For an introduction to regex, from a konsole:
 'khelpcenter help:/kate/regular-expressions.html'

Guidance on what the tqt regex engine supports is given in ntqregexp.html which will be installed to:
 '<TDE-installation-directory>/doc/tqt3-<tde-version>/ntqregexp.html'