re = /<([\w\-\/]+)( +[\w\-]+(=(('[^']*')|("[^"]*")))?)* *>/
str = ' </div><!-- SectionHeaderWrapper --><div id="SectionContent"><h3 id="sAdministrativeDataSummary" class="mDisabled">Administrative data</h3><h3 id="sWorkersHazardViaInhalationRoute">Workers - Hazard via inhalation route</h3><h4>Systemic effects</h4><h5>Long term exposure</h5><dl class="HorDL"><dt>Hazard assessment conclusion:</dt><dd>no hazard identified</dd></dl></dl></dl></dl></dl></dl><h5>Acute/short term exposure</h5><dl class="HorDL"><dt>Hazard assessment conclusion:</dt><dd>no hazard identified</dd></dl><h6>DNEL related information</h6></dl></dl></dl></dl></dl><h4>Local effects</h4><h5>Long term exposure</h5><dl class="HorDL"><dt>Hazard assessment conclusion:</dt><dd>DNEL (Derived No Effect Level)
Value:</dt><dd><span class="UserEntry">0.02</span> mg/m³
Most sensitive endpoint:</dt><dd>repeated dose toxicity</dd></dl><h6>DNEL related information</h6><dl class="HorDL"><dt>DNEL derivation method:</dt><dd>other: <span class="UserEntry">Biocidal Products Regulation guidance for Human Health Risk Assessment (Volume III, Part B, December 2013</span>'
subst = '\\n'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html