re = /<img src=([a-zA-Z0-9_\-\s\.\"=\/:%,()]*class=\"[a-zA-Z0-9_\-\s\.\"=\/:%,()]*lazy[a-zA-Z0-9_\-\s\.\"=\/:%,()]*)/m
str = ' <img src="fonts/608be7747d9cf15397b0d112_Logo-v3-01.svg" alt class="nav-logo">
<img src="images/6085e0acf284d920e7133043_Frame%201%20%283%29.png" loading="lazy" width="500" style="opacity:0" srcset="images/6085e0acf284d920e7133043_Frame%201%20%283%29-p-500.png 500w, images/6085e0acf284d920e7133043_Frame%201%20%283%29.png 738w" sizes="(max-width: 479px) 73vw, (max-width: 767px) 77vw, (max-width: 991px) 273.991455078125px, 380px" alt class="image_header">
<img src="images/6089c5d4b424624dc0cb450b_Frame%206.png" loading="lazy" width="263" sizes="(max-width: 479px) 65vw, (max-width: 767px) 77vw, (max-width: 991px) 33vw, 37vw" srcset="images/6089c5d4b424624dc0cb450b_Frame%206-p-500.png 500w, images/6089c5d4b424624dc0cb450b_Frame%206.png 651w" alt class="image_performance lazy">
<img src="images/6089c5d52359073cf4b6cc80_Frame%205.png" loading="lazy" width="287" sizes="(max-width: 479px) 77vw, (max-width: 767px) 85vw, (max-width: 991px) 41vw, 43vw" srcset="images/6089c5d52359073cf4b6cc80_Frame%205-p-500.png 500w, images/6089c5d52359073cf4b6cc80_Frame%205.png 771w" alt class="image_security lazy">
<img src="images/6089c5d4e99fbfce103ab502_Frame%207.png" loading="lazy" width="292" sizes="(max-width: 479px) 71vw, (max-width: 767px) 81vw, (max-width: 991px) 263.991455078125px, 370px" srcset="images/6089c5d4e99fbfce103ab502_Frame%207-p-500.png 500w, images/6089c5d4e99fbfce103ab502_Frame%207.png 651w" alt class="image_reliability lazy">
<img src="fonts/608be7747d9cf15397b0d112_Logo-v3-01.svg" alt class="footer-logo-copy lazy">
<img src="fonts/60857020dc3fb163eb8a7d19_icons8-instagram.svg" loading="lazy" alt class="instagram_logo lazy">'
subst = '<img data-src=$1'
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