Problem 1: Not many online/offline Regexp testing/debugging tools support Ruby Regexp syntax. But at the same time it's not very convenient to test Regexes right in your code or in the irb/pry (they are not interactive enough). Luckily we have Rubular, but…
Problem 2: Try to open Rubular and paste sample_data.txt content as a test string and regex.txt content as a regular expression. After matching highlight process is done (yeah, you have to be patient enough to see that) try to edit anything in Regexp…
Problem 3: Rubular currently supports Ruby 1.8.7 / 1.9.3 and 2.1.5, but it would be great to test your Regexes in your current Ruby version (just in case, to be 100% sure)
Problem 4: Sometimes highlighting ins't enough (because of a huge amount of the test data) it would be great to know exact count of occurrences.
This approach tastes better within tmux/screen with vim, but you could just place your GUI editor/IDE window side by side with the terminal.
$ watch -n1 -c ~/regex.sh ~/sample_data.txt
$ vim ~/regex.sh # or ~/regex.txt
#
# * Edit REGEX ENV variable export in the file or regex.txt content
# * (un)Comment lines in MODES section to affect the output
# * Use inline flags to ignore case and so on
# * If you have a complex regex use regex.txt file with (?x:<pattern>)
Check the demo!